Glossary of terms and abbreviations

This glossary defines technical terms and abbreviations used in the z/OS® Basic Skills Information Center.

If you do not find the term you are looking for, refer to the IBM® Glossary of Computing Terms, available from: http://www.ibm.com/ibm/terminology.

The following cross-references are used in this glossary:  Contrast with: This refers to a term that has an opposed or substantively different meaning.  See: This refers the reader to (a) a related term, (b) a term that is the expanded form of an abbreviation or acronym, or () a synonym or more preferred term.  Synonym for: This indicates that the term has the same meaning as a preferred term, which is defined in its proper place in the glossary.  Synonymous with: This is a reference from a defined term to all other terms that have the same meaning.  Obsolete term for: This indicates that the term should not be used and refers the reader to the preferred term.

This glossary includes terms and definitions from American National Standard Dictionary for Information Systems, ANSI X3.172-1990, copyright 1990 by the American National Standards Institute (ANSI). Copies may be purchased from the American National Standards Institute, 11 West 42nd Street, New York, New York 10036. Definitions are identified by an asterisk (*) that appears between the term and the beginning of the definition; a single definition taken from ANSI is identified by an asterisk after the item number for that definition.

© Copyright IBM Corp. 2006. All rights reserved. 1 2 Introduction to the New Mainframe: z/OS Basics access. The ability to read, update, or otherwise use a resource. Access to protected resources is usually controlled by system software. A access authority. An authority that relates to abend. abnormal end. a request for a type of access to protected resources. In RACF®, the access authorities abend dump. A kind of dump produced when are NONE, READ, UPDATE, ALTER, and a program ends abnormally. EXECUTE. abnormal end. End of a task, a , or a access control. In security, subsystem because of an error condition that ensuring that the resources of a computer cannot be resolved by recovery facilities while system can be accessed only by authorized the task is performed. See abnormal users in authorized ways. termination. access list. A list within a profile of all abnormal termination. (1) The end of authorized users and their access authorities. processing prior to scheduled termination. (2) A system failure or operator action that causes . A technique for moving data a job to end unsuccessfully. Synonymous with between main storage and I/O devices. abend, abnormal end. ACID properties. The properties of a ABR. area border node. transaction: atomicity, consistency, isolation, and durability. In CICS®, the ACID properties ACB. access control block. apply to a unit of work (UoW). accept. In SMP/E, to install SYSMODs in the ACK. acknowledgment field. distribution libraries. This is done with the ACCEPT command. Address Resolution Protocol (ARP). In the Internet suite of protocols, the protocol that ACCEPT command. The SMP/E command dynamically maps an IP address to an used to install SYSMODs in the distribution address used by a supporting metropolitan or libraries. local area network such as Ethernet or token-ring. accepted SYSMOD. A SYSMOD that has been successfully installed by the SMP/E address. The unique code assigned to each ACCEPT command. Accepted SYSMODs do device, or system connected to a not have the ERROR flag set and are found as network. SYSMOD entries in the distribution zone.

© Copyright IBM Corp. 2006. All rights reserved. 3 address space. A range of contiguous virtual Advanced Peer-to-Peer Networking® storage addresses that the system creates for (APPN). An extension to SNA featuring: (a) the user, batch job, or system task. In z/OS, an greater distributed network control that avoids address space can range up to 16 exabytes of critical hierarchical dependencies, thereby contiguous virtual storage addresses that the isolating the effects of single points of failure; system creates for the user. An address space (b) dynamic exchange of network topology contains user data and programs, as well as information to foster ease of connection, system data and programs, some of which are reconfiguration, and adaptive route selection; common to all address spaces. See virtual (c) dynamic definition of network resources; address space, data space. and (d) automated resource registration and directory lookup. APPN extends the LU 6.2 addressing mode (AMODE). A program peer orientation for end-user services to attribute that refers to the address length that network control and supports multiple LU is expected to be in effect when the program is types, including LU 2, LU 3, and LU 6.2. entered. In z/OS, addresses can be 24, 31, or 64 bits in length. Advanced Program-to-Program Communication (APPC). An implementation adjacent link station (ALS). In SNA, a link of the SNA LU 6.2 protocol that allows station directly connected to a given node by a interconnected systems to communicate and link connection over which network traffic can the processing of programs. be carried. AID. attention identifier. adjacent node. (1) In SNA, a node connected to another node by at least one path that AIW. APPN Implementation Workshop. connects no other node. (2) In OSI, a node that is attached to the same subnetwork as the alert. To cause the user's terminal to give local node. An adjacent node can be either a some audible or visual indication that an error destination node or a relay node. or some other event has occurred. adjacent subarea. A subarea connected by alias. An alternate label; for example, a label one or more links to another subarea with no and one or more aliases may be used to refer intervening subareas. See subarea. to the same data element or point in a . ADJSSCP. adjacent SSCP table. allocate. To assign a resource for use in administrator. A person responsible for performing a specific task. administrative tasks such as access authorization and content management. ALLOCATE command. In z/OS, the TSO/E Administrators can also grant levels of command that serves as the connection authority to users. between a file's logical name (the ddname) and the file's physical name (the name).

alphanumeric character. A letter or a number.

4 Introduction to the New Mainframe: z/OS Basics American Standard Code for Information application. A program or set of programs Interchange (ASCII). A standard code used that performs a task; some examples are for information exchange among data payroll, inventory management, and word processing systems, data communication processing applications. systems, and associated equipment. ASCII uses a coded character set consisting of 7-bit application layer. In the Open Systems coded characters. See Extended Binary Interconnection (OSI) reference model, the Coded Decimal Interchange Code (EBCDIC). layer that provides means for application processes residing in open systems to AMODE. addressing mode. exchange information and that contains the application-oriented protocols by which these anonymous user. A portal user who has not processes communicate. logged in to the portal with a valid user ID and password. application program. A collection of software components used to perform specific types of ANR. automatic network routing. work on a computer, such as a program that does inventory control or payroll. ANSI. American National Standards Institute. application programming interface (API). A AOR. application-owning region. software interface that enables applications to communicate with each other. An API is the APAR. authorized program analysis report. set of programming language constructs or APAR fix. A temporary correction of a defect statements that can be coded in an application in an IBM system control program or licensed program to obtain the specific functions and program that affects a specific user. An APAR services provided by an underlying operating fix is usually replaced later by a permanent system or service program. correction called a PTF. APAR fixes are application-instance DVIPA. A dynamic VIPA identified to SMP/E by the ++APAR statement. activated by an application that explicitly APF. authorized program facility. issues a bind() function call to the IP address.

APF-authorized. A type of system application-owning region (AOR). In a authorization using the authorized program CICSPlex® configuration, a CICS region facility (APF) that allows an installation to devoted to running applications. identify system or user programs that can use apply. In SMP/E, to install SYSMODs in the sensitive system functions. To maintain target libraries. This is done with the APPLY system security and integrity, a program must command. be authorized by the APF before it can access restricted functions, such as supervisor calls APPLY command. The SMP/E command (SVC) or SVC paths. used to install SYSMODs in the target libraries. API. application programming interface. APPN. Advanced Peer-to-Peer Network. APPC. advanced program-to-program communications.

5 APPN end node. A node that provides a ARM. automatic restart management. broad range of end-user services and supports sessions between its local control ARP. Address Resolution Protocol. point (CP) and the CP in an adjacent network node. It uses these sessions to dynamically ARPANET. A network established by the register its resources with the adjacent CP (its United States Department of Defense network node server), to send and receive Advanced Research Projects Agency (now the directory search requests, and to obtain Defense Advanced Research Projects management services. An APPN end node Agency). can also attach to other end nodes. See ASCII. American Standard Code for Advanced Peer-to-Peer Networking. Information Interchange. APPN network node. A node that offers a ASID. address space identifier. broad range of end-user services and that can provide the following: ASSEM entry. An SMP/E entry containing  Distributed directory services, including assembler statements that can be assembled registration of its domain resources to a to create an object module. central directory server  Topology database exchanges with other assembler. A computer program that converts APPN network nodes, enabling network assembler language instructions into binary nodes throughout the network to select machine language (object code). optimal routes for LU-LU sessions based assembler language. A symbolic on requested classes of service programming language that comprises  Session services for its local LUs and client instructions for basic computer operations end nodes. which are structured according to the data See Advanced Peer-to-Peer Networking. formats, storage structures, and registers of the computer. APPN network. A collection of interconnected network nodes and their client end nodes. See asynchronous processing. A series of Advanced Peer-to-Peer Networking. operations that are done separately from the job in which they were requested; for example, APPN node. An APPN network node or an submitting a batch job from an interactive job APPN end node. at a work station. See synchronous processing. ARB flow. adaptive rate-based flow. Asynchronous Transfer Mode (ATM). A area border router (ABR). Routers that transfer mode in which the information is attach to more than one area. All area border organized into cells. It is asynchronous in the routers are part of the backbone, so they must sense that the recurrence of cells containing either attach directly to a backbone IP subnet information from an individual user is not or be connected to another backbone router necessarily periodic. ATM is specified in over a virtual link. international standards such as ATM Forum UNI 3.1.

6 Introduction to the New Mainframe: z/OS Basics ATM. (1) Asynchronous Transfer Mode. (2) automatic call. The used by the automatic teller machine. linkage editor to resolve external symbols left undefined after all the primary input has been AT-TLS. Application Transparent Transport processed. See automatic call . Layer Security. automatic call library. Contains load modules audit. To review and examine the activities of or object decks that are to be used as a data processing system mainly to test the secondary input to the linkage editor to resolve adequacy and effectiveness of procedures for external symbols left undefined after all the data security and data accuracy. primary input has been processed. The automatic call library can be: authentication. In computer security, verification of the identity of a user or process  Libraries containing object decks, with or and the construction of a data structure that without linkage editor control statements contains the privileges that were granted to the  Libraries containing load modules user or process.  The library containing Language Environment® runtime routines. authority. The right to access objects, resources, or functions. automatic library call. Automatic call. See automatic call library. authorization. The process of granting a user either complete or restricted access to an automatic restart. A restart that takes place object, resource, or function. during the current run, that is, without resubmitting the job. An automatic restart can authorization checking. The action of occur within a job step or at the beginning of a determining whether a user is permitted job step. Contrast with deferred restart. See access to a RACF-protected resource. checkpoint restart. authorized program analysis report automatic restart management. A z/OS (APAR). A request for correction of a problem recovery function that improves the availability caused by a defect in a current unaltered of batch jobs and started tasks. When a job release of a program. The correction is called fails, or the system on which it is running an APAR fix. unexpectedly fails, z/OS can restart the job without operator intervention. authorized program facility (APF). A facility that permits identification of programs automation. A program or facility that authorized to use restricted functions. performs certain operations automatically in response to system events or user automated operations. Automated preferences. procedures to replace or simplify actions of operators in both systems and network auxiliary storage. All addressable storage operations. other than processor storage.

7 availability. The degree to which a system or backout. A request to remove all changes to resource is ready when needed to process resources since the last commit or backout or, data; the percentage of time a system, for the first unit of recovery, since the network, or component can be utilized, within beginning of the application. Backout is also a certain time frame. Generally, the called rollback or abort. percentage is derived by dividing actual availability time by scheduled availability time. backplane. A circuit board that connects Scheduled outages (no service periods) are several connectors in parallel to each other, so not counted against the availability that each pin of each connector is linked to the measurement. A service may be unavailable same relative pin of all the other connectors, even though the components used to provide forming a computer bus. the service are all available, and vice-versa. backup. (1) Pertaining to a system, device, file, or facility that can be used in the event of a malfunction or loss of data. (2) The process of B creating a copy of a data set to ensure against accidental loss. backbone. (1) A set of nodes and their interconnecting links providing the primary backup host. A host that is designated as a data path across a network. (2) In a local area backup in the event that the distributing host network multiple-bridge ring configuration, a should malfunction. The backup host takes high-speed link to which the rings are over the IP address of the distributing host connected by means of bridges or routers. A when required. See distributing host. backbone may be configured as a bus or as a ring. (3) In a wide area network, a high-speed BAL. Basic Assembler Language. link to which nodes or data switching exchanges (DSEs) are connected. bandwidth. (1) The capacity of a communications line, normally expressed in background. (1) In multiprogramming, the bits per second (bps). (2) A measure of the environment in which low-priority programs capacity of a communication transport are executed. (2) Under TSO/E the medium (such as a TV cable) to convey data. environment in which jobs submitted through (3) Data rate transfer in K bits, K bytes, M bits, the SUBMIT command or SYSIN are and M bytes per second. (4) In asynchronous executed. One job step at a time is assigned to transfer mode (ATM), the capacity of a virtual a region of central storage, and it remains in channel, expressed in terms of peak rate central storage to completion. Contrast with (PCR), sustainable cell rate (SCR), and foreground. maximum burst size (MBS). background job. (1) A low-priority job, usually base function. In SMP/E, a SYSMOD a batched or non-interactive job. (2) Under defining elements of the base z/OS system or TSO, a job entered through the SUBMIT other products that were not previously command or through SYSIN. Contrast with present in the target libraries. Base functions foreground job. are identified to SMP/E by the ++FUNCTION statement. SMP/E itself is an example of a base function of z/OS.

8 Introduction to the New Mainframe: z/OS Basics base level system. In SMP/E, the level of the big endian. A format for the storage of binary target system modules, macros, source, and data in which the most significant byte is DLIBs created by system generation, to which placed first. Big endian is used by most function and service modifications are hardware architectures including the applicable. z/Architecture™. Contrast with little endian. basic information unit (BIU). In SNA, the unit binary data. (1) Any data not intended for of data and control information passed direct human reading. Binary data may contain between half-sessions. It consists of a unprintable characters, outside the range of request/response header (RH) followed by a text characters. (2) A type of data consisting of request/response unit (RU). numeric values stored in bit patterns of 0s and 1s. Binary data can cause a large number to batch job. A predefined group of processing be placed in a smaller space of storage. actions submitted to the system to be performed with little or no interaction between bind. (1) To combine one or more control the user and the system. Contrast with sections or program modules into a single interactive job. program module, resolving references between them. (2) A connection between batch message processing (BMP) program. systems or logical units. (3) In SNA, a request An IMS™ program that has to activate a session between two logical units access to online databases and message (LUs). queues. BMPs run online, but like programs in a batch environment, they are started with job binder. The z/OS program that processes the (JCL). output of the language translators and compilers into an executable program (load batch processing. A method of running a module or program object). It replaces the program or a series of programs in which one linkage editor and batch used in earlier or more records (a batch) are processed with forms of the z/OS , such as little or no action from the user or operator. MVS™ and OS/390®. Contrast with interactive processing. BLK. A subparameter of the SPACE batch. A group of records or data processing parameter in a statement. It specifies that jobs brought together for processing or space is allocated by blocks. transmission. Pertaining to activity involving little or no user action. Contrast with BLKSIZE. block size. interactive. BLOB. binary large object. BCP. base control program. block. (1) A set of consecutive pages on disk. BEX. branch extender. (2) A unit of data storage on a device. (3) A set of contiguous pages in a buffer pool. (4) A string of data elements that is recorded or transmitted as a unit. (5) A sequence of text, commands, or records that are read, written, or processed as a unit.

9 block size. (1) The number of data elements bridge. A functional unit that interconnects in a block. (2) A measure of the size of a block, multiple LANs (locally or remotely) that use the usually specified in units such as records, same logical link control protocol, but that can words, computer words, or characters. use different medium access control protocols. Synonymous with block length and physical A bridge forwards a frame to another bridge record size. based on the medium access control (MAC) address. book package. In IBM mainframes, a pre-assembled collection of physical hardware BrNN. branch network node. that is installed in the central processor complex (CPC) cage. This hardware collection broadcast. (1) Transmission of the same data consists of processor chips, memory cards, to all destinations. (2) Simultaneous and adapter cards that connect the processors transmission of data to more than one and memory to input/output devices. destination. (3) Contrast with multicast. border node. An APPN network node that broadcast search. The propagation of a interconnects APPN networks having search request, when the location of a independent topology databases in order to resource is unknown to the requester, to all support LU-LU sessions between these network nodes in an APPN network. Contrast networks. See extended border node, with directed Locate search. peripheral border node. BSAM. basic sequential access method. boundary function (BF). In SNA, a capability of a subarea node to provide protocol support buffer. (1) A portion of storage used to hold for attached peripheral nodes, such as: (a) input or output data temporarily. (2) An area of interconnecting subarea path control and storage that compensates for the different peripheral. speeds of data flow or timings of events by temporarily holding a block of data that is BPAM. basic partitioned access method. waiting to be processed or written to an I/O device. branch extender. An extension to the APPN network architecture that appears as a buffer pool. An area of memory into which network node to the downstream end nodes in data pages are read, modified, and held low entry networks and as an end node to the during processing. wide area network. bus. A facility for transferring data between branch network node (BrNN). See branch several devices located between two end extender. points, with only one device being able to transmit at a given moment. BrEx. branch extender. BX. branch extender.

10 Introduction to the New Mainframe: z/OS Basics bypass. In SMP/E, to circumvent errors that cache structure. A coupling facility structure would otherwise cause SYSMOD processing that enables high-performance sharing of to fail. This is done by using the BYPASS cached data by multisystem applications in a operand on an SMP/E command. sysplex. Applications can use a cache structure to implement several different types byte multiplexer channel. A multiplexer of caching systems, including a store-through channel that interleaves bytes of data. or a store-in cache. byte stream. A simple sequence of bytes cage. An area within a frame that contains stored in a stream file. Contrast with record hardware elements required for either data. processing or input/output (I/O) capability. See I/O cage.

called routine. A routine or program that is C invoked by another.

C language. A high-level language used to capacity. A measure of how much volume can develop software applications in compact, be handled by a specific resource. efficient code that can be run on different types of with minimal change. carriage control character. An optional character in an input data record that specifies CA. certificate authority. a write, space, or skip operation. cabinet. Housing for panels organized into carriage return (CR). (1) A keystroke port groups of patchports, which are pairs of generally indicating the end of a command fibre adapters or couplers. Cabinets are used line. (2) In text data, the action that indicates to to organize long, complex cables between continue printing at the left margin of the next processors and controllers, which may be as line. (3) A character that will cause printing to far away as another physical site. Also known start at the beginning of the same physical line as fiber management cabinets. in which the carriage return occurred. cable “in inventory.” Unused cables. Carrier Sense Multiple Access with Collision Detection (CSMA/CD). A media cache. A special-purpose buffer storage, access method that monitors another station's smaller and faster than main storage, used to transmissions. If the data station detects hold a copy of instructions and data obtained another signal during transmission, it stops from main storage and likely to be needed next transmitting, sends a jam signal, then waits for by the processor. a variable time before trying again.

CART. command and response token.

case-sensitive. Pertaining to the ability to distinguish between uppercase and lowercase letters.

11 catalog. (1) A directory of files and libraries, central processing unit (CPU). Synonymous with reference to their locations. (2) To enter with processor. information about a file or a library into a catalog. (3) The collection of all data set central processor (CP). The part of the indexes that are used by the control program computer that contains the sequencing and to locate a volume containing a specific data processing facilities for instruction execution, set. initial program load, and other machine operations. cataloged data set. A data set that is represented in an index or hierarchy of indexes central processor complex (CPC). A that provide the means for locating it. physical collection of hardware that consists of main storage, one or more central processors, cataloged procedure. A set of timers, and channels. language (JCL) statements placed in a library and retrievable by name. central storage. (1) In z/OS, the storage of a computing system from which the central CCL. Communications Controller for ®. processing unit can directly obtain instructions and data, and to which it can directly return CCW. channel command word. results. (Formerly referred to as “real storage”.) (2) Synonymous with processor CDLC. Channel Data Control Link protocol. storage.

CDRM. cross-domain resource manager. CF. coupling facility

CDRSC. cross-domain resource. CFRM. coupling facility resource management. CDS. central directory server. CGI. Common Gateway Interface. CEC. central electronic complex. channel. In mainframe computing, the part of CEMT. The CICS-supplied transaction that a channel subsystem that manages a single allows checking of the status of terminals, I/O interface between a channel subsystem connections, and other CICS entities from a and a set of control units. Each channel is an console or from CICS terminal sessions. independent unit that transfers data central directory server. A network node that concurrently with other channels and the CPU. provides a repository for information on For example, in a 64-channel computer, 64 network resource locations; it also reduces the streams of data are transferred number of network searches by providing a simultaneously. In contrast, the bus in a focal point for queries and broadcast desktop computer is a shared channel searches, and by caching the results of between all devices plugged into it. network searches to avoid later broadcasts for channel adapter. A device that groups two or the same information. more controller channel interfaces central electronic complex (CEC). Obsolete electronically. term for central processor complex (CPC).

12 Introduction to the New Mainframe: z/OS Basics channel connection address (CCA). The character. A letter, digit, or other symbol. A input/output (I/O) address that uniquely letter, digit, or other symbol that is used as part identifies an I/O device to the channel during of the organization, control, or representation an I/O operation. of data. A character is often in the form of a spatial arrangement of adjacent or connected channel interface. The circuitry in a storage strokes. control that attaches storage paths to a host channel. checkpoint. (1) A place in a routine where a check, or a recording of data for restart channel path. In mainframe computing, the purposes, is performed. (2) A point at which interconnection between a channel and its information about the status of a job and the associated control units. system can be recorded so that the job step can be restarted later. channel path identifier. The logical equivalent of channels in the physical checkpoint data set. A data set in which processor. information about the status of a job and the system can be recorded so that the job step channel subsystem (CSS). A collection of can be restarted later. subchannels that directs the flow of information between I/O devices and main checkpoint write. Any write to the checkpoint storage, relieves the processor of data set. A general term for the primary, communication tasks, and performs path intermediate, and final writes that update any management functions. checkpoint data set. channel-to-channel (CTC). The CHPID. channel path identifier. communication (transfer of data) between programs on opposite sides of a CI. control interval. channel-to-channel adapter (CTCA). CICS. Customer Information Control System. channel-to-channel adapter (CTCA). An input/output device that is used a program in CICSplex. A configuration of interconnected one system to communicate with a program in CICS systems in which each system is another system. dedicated to one of the main elements of the overall workload. See application owning channel-to-channel connection. A region and terminal owning region. connection between two CHPIDs on the same or different processors, either directly or CIP. channel interface processor. through a switch. When connecting through a switch, both CHPIDs must be connected circuit switching. A process that, on demand, through the same or a chained switch. connects two or more data terminal equipment (DTEs) and permits the exclusive use of a data circuit between them until the connection is released. Synonymous with line switching. See packet switching.

13 CKD. count-key data. code page. (1) An assignment of graphic characters and control function meanings to all CLAW. Common Link Access to Workstation. code points; for example, assignment of characters and meanings to 256 code points client. A system or process that is dependent for an 8-bit code, assignment of characters on another system or process (usually called and meanings to 128 code points for a 7-bit the server) to provide it with access to data, code. (2) A particular assignment of services, programs, or resources. See identifiers to graphic characters. client-server, server. code point. A 1-byte code representing one of client-server. In TCP/IP, the model of 256 potential characters. interaction in distributed data processing in which a program at one site sends a request to coexistence. Two or more systems at different a program at another site and awaits a levels (for example, software, service or response. The requesting program is called a operational levels) that share resources. client; the answering program is called a Coexistence includes the ability of a system to server. respond in the following ways to a new function that was introduced on another CLIST. command list. system with which it shares resources: ignore a new function; terminate gracefully; support a CLOB. character large object. new function. CLPA. create link pack area. collision. An unwanted condition that results cluster. A group of interconnected computers from concurrent transmissions on a channel, that are working together as one unit. causing the transmissions to be unintelligible.

CMOS. complementary metal-oxide command. A request to perform an operation semiconductor. or run a program. When parameters, arguments, flags, or other operands are CMS. Conversational Monitor System. associated with a command, the resulting character string is a single command. CMT. CHPID mapping tool. command and response token (CART). A CNN. composite network node. parameter on WTO, WTOR, MGCRE, and certain TSO/E commands and execs COBOL. Common Business-Oriented that allows you to link commands and their Language. associated message responses.

command prefix. A one- to eight-character command identifier. The command prefix distinguishes the command as belonging to an application or subsystem rather than to z/OS.

COMMAREA. A communication area made available to applications running under CICS.

14 Introduction to the New Mainframe: z/OS Basics commit. A request to make all changes to Communications Server. IBM software that resources since the last commit or backout or, supports (a) the development and use of for the first unit of recovery, since the application programs among two or more beginning of the application. connected systems or , (b) multiple concurrent connections that use a Common Business-Oriented Language wide range of protocols, and (c) several (COBOL). A high-level language, based on application programming interfaces () that English, that is primarily used for business may be called concurrently and that are applications. designed for client/server and distributed application programs. Communications Server common service area (CSA). In z/OS, a part includes the necessary interfaces for network of the common area that contains data areas management and is available on several that are addressable by all address spaces. operating systems (such as AIX®, z/OS, and Windows® NT). z/OS Communications Server communication controller. A type of is not available as a stand-alone product. communication control unit whose operations Rather, it is an element of the z/OS operating are controlled by one or more programs stored system. z/OS Communications Server and executed in the unit. It manages the includes the function of these former IBM details of line control and the routing of data products: TCP/IP for MVS/ESA™ and VTAM® through a network. for MVS/ESA. The VTAM for MVS/ESA communication line. Deprecated term for function is called Communications Server - telecommunication line. SNA Services, and the TCP/IP for MVS/ESA function is called Communications Server - IP Communications Controller for Linux Services. (CCL). A software product for mainframe servers that emulates the IBM 3745 Communications Storage Manager (CSM). Communication Controller hardware. In z/OS Communications Server, a buffer management technology that reduces performance overhead resulting from the movement of large amounts of data. CSM enables authorized host application programs to put data in buffers that can be addressed and accessed by other authorized host application programs without any need to copy the data.

compatibility. Ability to work in the system or ability to work with other devices or programs.

compilation unit. A portion of a computer program sufficiently complete to be compiled correctly.

15 compiler. A program that translates a source condition code. A code that reflects the result program into an executable program (an object of a previous input/output, arithmetic, or logical deck). operation. compiler options. Keywords that can be configuration. The arrangement of a specified to control certain aspects of computer system or network as defined by the compilation. Compiler options can control the nature, number, and chief characteristics of its nature of the load module generated by the functional units. compiler, the types of printed output to be produced, the efficient use of the compiler, connection. (1) In data communications, an and the destination of error messages. Also association established between functional called compiler-time options. units for conveying information. (2) TCP/IP, the path between two protocol applications that complementary metal oxide semiconductor provides reliable data stream delivery service. (CMOS). A technology that combines the In Internet communications, a connection electrical properties of n-type semiconductors extends from a TCP application on one system and p-type semiconductors. to a TCP application on another system. component. A functional part of an operating connectionless protocol. A transport system; for example, the scheduler or protocol, such as UDP, that does not require a supervisor. connection to be established prior to data transfer. component trace. A service that provides a way for z/OS components to collect problem connection-oriented protocol. A protocol data about events. requiring establishment of a session prior to data transfer. composite network node. A type 5 node and its subordinate type 4 nodes that support connectivity. (1) The capability of a system or APPN network node protocols and appear to device to be attached to other systems or an attached APPN or LEN node as a single devices without modification. (2) The capability network node. to attach a variety of functional units without modifying them. concentrator. (1) In data transmission, a functional unit that permits a common consistent copy. A copy of data entity (for transmission medium to serve more data example, a logical volume) that contains the sources than there are channels currently contents of the entire data entity from a single available within the transmission medium. (2) instant in time. Any device that combines incoming messages into a single message (concentration) or console. An input/output device on a extracts individual messages from the data computer, reserved for communication sent in a single transmission sequence between the computer operator or (deconcentration). maintenance engineer and the computer.

16 Introduction to the New Mainframe: z/OS Basics console group. In z/OS, a group of consoles control unit (CU). A device that coordinates defined in CNGRPxx, each of whose members and controls the operation of one or more can serve as an alternate console in console input/output devices, and synchronizes the or hardcopy recovery or as a console to operation of such devices with the operation of display synchronous messages. the system as a whole. Each physical controller contains one or more logical control control block. A storage area used by a units, channel and device interfaces, and a computer program to hold control information. power source. Controllers can be divided into segments, or grouped into subsystems. control interval (CI). A fixed-length area or Synonymous with controller or device control disk in which VSAM stores records and unit. creates distributed free space. Also, in a key-sequenced data set or file, the set of control unit address. The high order bits of records that an entry in the sequence-set the storage control address, used to identify index record points to. The control interval is the storage control to the host system. the unit of information that VSAM transmits to or from disk. A control interval always includes controller. Synonymous with control unit. an integral number of physical records. convergence. The recognition of changes in a control region. The main storage region that network by a dynamic routing protocol. contains the subsystem work manager or subsystem resource manager control conversation. A logical connection between program. two programs over an LU type 6.2 session that allows them to communicate with each other control section (CSECT). The part of a while processing a transaction. program specified by the programmer to be a relocatable unit, all elements of which are to conversational. Pertaining to a program or a be loaded into adjoining main storage system that carries on a dialog with a terminal locations. user, alternately accepting input and then responding to the input quickly enough for the control statement. In programming user to maintain a train of thought. languages, a statement that is used to alter the continuous sequential execution of conversational monitor system (CMS). A statements; a control statement can be a virtual machine operating system that provides conditional statement, such as IF, or an general interactive time sharing, problem imperative statement, such as STOP. In JCL, a solving, and program development statement in a job that is used in identifying capabilities, and operates only under the the job or describing its requirements to the control of the VM/370 control program. operating system. CORBA. Common Object Request Broker Architecture.

17 corequisite SYSMODs. SYSMODs each of CPC. central processor complex. which can be installed properly only if the other is present. Corequisites are defined by CP-CP session. A parallel session between the REQ operand on the ++VER statement. two control points, using LU 6.2 protocols and a mode name of CPSVCMG, on which corrective service. Any SYSMOD used to network services requests and replies are selectively fix a system problem. Generally, exchanged. Each CP of a given pair has one corrective service refers to APAR fixes. contention-winner session and one contention-loser session with the other. CoS. class of service. CPU. central processing unit. count-key data. A disk storage device for storing data in the format: count field normally create link pack area (CLPA). An option that followed by a key field followed by the actual is used during IPL to initialize the link pack data of a record. The count field contains, in pageable area. addition to other information, the address of the record in the format: CCHHR (where CC is crossbar switch. A static switch that can the two-digit cylinder number, HH is the connect controllers to processors with parallel two-digit head number, and R is the record (bus and tag) interfaces. The crossbar number) and the length of the data. The key contains a number of channel interfaces on its field contains the record's key. top, which can connect to objects above it such as processors or other crossbars. The couple data set. A data set that is created crossbar switch also contains a number of through the XCF couple data set format utility control unit interfaces on its side, which can and, depending on its designated type, is connect to objects below it such as controllers shared by some or all of the z/OS systems in a or other crossbars. sysplex. See sysplex couple data set. cross-domain resource manager (CDRM). coupling facility. A special In VTAM, the function in the system services that provides high-speed caching, list control point (SSCP) that controls initiation processing, and locking functions in a sysplex. and termination of cross-domain sessions. coupling facility channel. A high bandwidth cross-memory linkage. A method for fiber optic channel that provides the invoking a program in a different address high-speed connectivity required for data space. The invocation is synchronous with sharing between a coupling facility and the respect to the caller. central processor complexes directly attached to it. cross-system coupling facility (XCF). A component of z/OS that allows authorized coupling services. In a sysplex, the functions programs to communicate channel-to-channel, of XCF that transfer data and status between peer-to-peer, across a sysplex. XCF supports members of a group residing on one or more program communication and sends program z/OS systems in the sysplex. status and signal information between z/OS system images in a sysplex. CP. (1) central processor. (2) control point.

18 Introduction to the New Mainframe: z/OS Basics cross-system extended services (XES). A cumulative service tape. A tape sent with a set of z/OS services that allow multiple new function order, containing all current PTFs instances of an application or subsystem, for that function. running on different systems in a sysplex environment, to implement high-performance, Customer Information Control System | high-availability data sharing by using a (CICS). An online transaction processing coupling facility. (OLTP) system that provides specialized interfaces to databases, files and terminals in cross-system restart. If a system fails, support of business and commercial automatic restart management restarts applications. CICS enables transactions elements on another eligible system in the entered at remote terminals to be processed sysplex. concurrently by user-written application programs. CRU. customer-replaceable unit. customer-replaceable unit (CRU). An cryptographic key. A parameter that assembly or part that a customer can replace determines cryptographic transformations in its entirety when any of its components fail. between plaintext and ciphertext. See field-replaceable unit. cryptography. The transformation of data to cylinder. (1) A unit of storage on a conceal its meaning. count-key-data (CKD) device with a fixed number of tracks. (2) On a magnetic disk or in CSA. common service area. an assembly of disks, the set of all tracks that can be accessed by all the magnetic heads of CSCL. carrier-supplied communication line. a comb in a given position, without CSECT. control section. repositioning the access mechanism.

CSI. consolidated software inventory data set. See SMPCSI. D CSM. Communications Storage Manager. daemon. In ® systems, a long-lived CSMA/CD. carrier sense multiple access with process that runs unattended to perform collision detection. continuous or periodic system-wide functions, such as network control. Some daemons are CSS. channel subsystem. triggered automatically to perform their task; others operate periodically. An example is the CTC. channel-to-channel. cron daemon, which periodically performs the tasks listed in the crontab file. The z/OS CTC connection. channel-to-channel equivalent is a started task. connection. DAF. destination address field. CTRACE. component trace. DASD. direct access storage device. CU. control unit.

19 DASD volume. A DASD space identified by a data in transit. The update data on common label and accessed by a set of application system DASD volumes that is related addresses. See volume. being sent to the recovery system for writing to DASD volumes on the recovery system. data class. A collection of allocation and space attributes, defined by the storage data integrity. The condition that exists when administrator, that are used that are used accidental or intentional destruction, alteration, when allocating a new SMS-managed data or loss of data does not occur. set. data link control (DLC). A set of rules used data communication. The process of sending by nodes on a data link (such as an SDLC link or receiving data between two points of a or a token ring) to accomplish an orderly network. exchange of information. (DCB). A control block data link layer. In the Open Systems used by access method routines in storing and Interconnection reference model, the layer that retrieving data. provides services to transfer data between entities in the network layer over a data definition name (ddname). (1) The communication link. The data link layer name of a data definition (DD) statement that detects, and possibly corrects, errors that may corresponds to a data control block that occur in the physical layer. contains the same name. (2) The symbolic representation for a name placed in the name data link switching (DLSw). A method of field of a data definition (DD) statement. transporting network protocols that use IEEE 802.2 logical link control (LLC) type 2. SNA data definition statement. A JCL control and NetBIOS are examples of protocols that statement that serves as the connection use LLC type 2. See encapsulation, spoofing. between a file's logical name (the ddname) and the file's physical name (the data set data set. In z/OS, a named collection of name). related data records that is stored and retrieved by an assigned name. Equivalent to data division. In COBOL, the part of a a file in other operating systems. program that describes the files to be used in the program and the records contained within data set backup. Backup to protect against the files. It also describes any the loss of individual data sets. WORKING-STORAGE data items, LINKAGE SECTION data items, and LOCAL-STORAGE data set label. (1) A collection of information data items that are needed. that describes the attributes of a data set and is normally stored on the same volume as the Data Facility Sort (DFSORT™). An IBM data set. (2) A general term for data set control licensed program that is a high-speed blocks and tape data set labels. data-processing utility. DFSORT provides a method for sorting, merging, and copying operations, as well as providing versatile data manipulation at the record, field, and bit level.

20 Introduction to the New Mainframe: z/OS Basics data sharing. The ability of concurrent database management system (DBMS). A subsystems (such as DB2® or IMS DB) or software system that controls the creation, application programs to directly access and organization, and modification of a database change the same data, while maintaining data and the access to the data that is stored in it. integrity. datagram. In packet switching, a data space. z/OS shared memory, somewhat self-contained packet, independent of other like shared memory regions in POSIX. A data packets, which carries information sufficient for space contains data only, which can be shared routing from the originating data terminal by multiple address spaces (users) without equipment (DTE) to the destination DTE inadvertently being modified. without relying on earlier exchanges between the DTEs and the network. data stream. (1) A continuous stream of data elements being transmitted, or intended for DB2. DATABASE 2; an IBM relational transmission, in character or binary-digit form, database management system. using a defined format. (2) All information (data and control commands) sent over a data DB2 data sharing group. A collection of one link usually in a single read or write operation. or more concurrent DB2 subsystems that For example, a data stream is used to send directly access and change the same data displays and to receive displays from a while maintaining data integrity. workstation device. DBCS. double-byte character set. data type. The properties and internal representation that characterize data. DBMS. database management system. data warehouse. A system that provides DC. data communication. critical business information to an DCB. data control block. organization. The data warehouse system cleanses the data for accuracy and currency, DCLGEN. declarations generator. and then presents the data to decision makers so that they can interpret and use it effectively DD card. Deprecated term for DD statement. and efficiently. DD statement. data definition statement. database. A collection of interrelated or independent data items that are stored ddname. data definition name. together to serve one or more applications. database administrator (DBA). (1) A person who is responsible for the design, development, operation, security, maintenance, and use of a database. (2) A DB2 UDB user with DBADM authority.

21 deadlock. (1) An error condition in which dependent LU requester (DLUR). An APPN processing cannot continue because each of end node or network node that: (a) owns two elements of the process is waiting for an dependent LUs in its local node or in action by or a response from the other. (2) adjacently attached nodes; and (b) obtains Unresolvable contention for the use of a SSCP services for these dependent LUs from resource. (3) An impasse that occurs when a dependent LU server (DLUS) located multiple processes are waiting for the elsewhere in an APPN network. The flows of availability of a resource that does not become SSCP services between DLUR and DLUS are available because it is being held by another encapsulated in APPN formats and carried process that is in a similar wait state. over a special pair of LU 6.2 sessions (referred to as a CP-SVR pipe). deallocate. To release a resource that is assigned to a specific task. dependent LU server (DLUS). An APPN network node that provides SSCP services for declarations generator (DCLGEN). A dependent LUs owned by dependent LU subcomponent of DB2 that generates SQL requesters (DLURs) located elsewhere in an table declarations and COBOL, C, or PL/I data APPN network. structure declarations that conform to the table. The declarations are generated from destination. (1) A combination of a node DB2 system catalog information. name and one of the following: a user ID, a remote printer or punch, a special local printer, dedicated. Pertaining to the assignment of a or LOCAL (the default if only a node name is system resource—a device, a program, or a specified). (2) Any point or location, such as a whole system—to an application or purpose. node, station, or a particular terminal, to which information is to be sent. (3) An external default. A value that is used or an action that logical unit (LU) or application program to is taken when no alternative is explicitly which messages or other data are directed. specified by the user. destination node. The node that provides deferred restart. A restart performed by the application services to an authorized external system when a user resubmits a job. The user. operator submits the restart deck to the system through a system input reader. See device. A computer peripheral or an object checkpoint restart. Contrast with automatic that appears to the application as such. restart. device address. The field of an ESCON® deleted function. In SMP/E, a function that device-level frame that selects a specific was removed from the system when another device on a control unit image. The one or two function was installed. This is indicated by the left-most digits are the address of the channel DELBY subentry in the SYSMOD entry for the to which the device is attached. The two deleted function. rightmost digits represent the unit address. dependent LU. See SSCP-dependent LU. device control unit. A hardware device that controls the reading, writing, or displaying of data at one or more I/O devices or terminals.

22 Introduction to the New Mainframe: z/OS Basics device number. A four-hexadecimal-character Dijkstra's shortest path algorithm. An identifier, for example 13A0, that you associate algorithm named after E.W. Dijkstra that finds with a device to facilitate communication the shortest path from a source to a between the program and the host operator. destination. The device number that you associate with a subchannel. direct access storage device (DASD). A device in which the access time is effectively Device Support Facilities program independent of the location of the data. (ICKDSF). A program used to initialize DASD volumes at installation and perform media direct memory access (DMA). The system maintenance. facility that allows a device to get direct access to the system or bus memory without the device type. The general name for a kind of intervention of the system processor. device; for example, 3390. directed Locate search. A search request DFS™. Distributed File Service. sent to a specific destination node known to contain a resource, such as a logical unit, to DFSMS. Data Facility Storage Management verify the continued presence of the resource Subsystem. at the destination node and to obtain the node's connectivity information for route DFSMShsm™. An IBM product used for calculation. Contrast with broadcast search. backing up and recovering data, and Synonymous with directed search. managing space on volumes in the storage hierarchy. directory. (1) A type of file containing the names and controlling information for other DFSORT. Data Facility Sort. files or other directories. Directories can also contain subdirectories, which can contain dialog. An interactive pop-up window subdirectories of their own. (2) A file that containing options that allow you to browse or contains directory entries. No two directory modify information, take specific action entries in the same directory can have the relating to selected objects, or access other same name. (POSIX.1). (3) A file that points to dialogs. For example, HCM provides a series files and to other directories. (4) An index used of dialogs to help you create, edit, delete, and by a control program to locate blocks of data connect objects, as well as manipulate the that are stored in separate areas of a data set configuration diagram. in direct access storage. digital certificate. An electronic document disabled wait state. Pertaining to a state of a used to identify an individual, server, company, processing unit that prevents the occurrence or some other entity, and to associate a public of certain types of interruptions. key with the entity. A digital certificate is issued by a certification authority and is digitally signed by that authority.

23 disaster recovery. Recovery after a disaster, Distributed File Service (DFS). A DCE such as a fire, that destroys or otherwise component. DFS joins the local file systems of disables a system. Disaster recovery several file server machines making the files techniques typically involve restoring data to a equally available to all DFS client machines. second (recovery) system, then using the DFS allows users to access and share files recovery system in place of the destroyed or stored on a file server anywhere in the disabled application system. See recovery, network, without having to consider the backup, recovery system. physical location of the file. Files are part of a single, global namespace, so that a user can disk. A storage device that includes one or be found anywhere in the network by means of more flat, circular plates with magnetic or the same name. optical surfaces on which information is stored. distributing host. The designated contact DISP. Disposition; a JCL DD parameter. (point of entry) for a sysplex. The distributing host is the normal owner of the IP address that dispatch. (1) To allocate processing time on a clients out in the network use to connect to the specific device for a job that is ready to run. (2) sysplex. In CICS, to schedule a task for execution. Dispatching is done by CICS task control. See distribution library (DLIB). A library that service request block. contains the master copy of all the elements in a system. A distribution library can be used to dispatching priority. A number assigned to create or back up a target library. tasks, used to determine the order in which they are to use the processor in a multitasking distribution zone. In SMP/E, a group of environment such as z/OS. records in a CSI data set that describes the SYSMODs and elements in a distribution display console. In z/OS, an MCS console library. whose input/output function you can control. DLIB. distribution library. distributed computing. Computing that involves the cooperation of two or more DLL. dynamic link library. machines communicating over a network. Data and resources are shared among the DLSw. data link switching. individual computers. DLU. destination logical unit. Distributed Computing Environment (DCE). A comprehensive, integrated set of services DLUR. dependent LU requester. that supports the development, use, and maintenance of distributed applications. DCE DLUS. dependent LU server. is independent of the operating system and DMA. direct memory access. network; it provides interoperability and portability across heterogeneous platforms. DNS. domain name server. distributed data. Data that resides on a DBMS other than the local system.

24 Introduction to the New Mainframe: z/OS Basics domain. (1) In SNA communications, the dump. (1) A report showing the contents of network resources under control of a particular storage. Dumps are typically produced system services control point (SSCP). (2) A following program failures, for use as part of a network that is administered as a unit diagnostic aids. (2) To copy the contents of all with a common protocol. or part of storage for the purpose of collecting error information. (3) Data that has been domain name server. In the Internet suite of dumped. protocols, a server program that supplies name-to-address translation by mapping duplex. Pertaining to communication in which domain names to IP addresses. Synonymous data can be sent and received at the same with name server. time. Synonymous with full-duplex. Contrast with half-duplex. double-byte character set (DBCS). A set of characters in which each character is DVIPA. Dynamic Virtual IP Address. represented by a two-bytes code. Languages such as Japanese, Chinese, and Korean, dynamic allocation. Assignment of system which contain more symbols than can be resources to a program at the time the represented by 256 code points, require program is executed rather than at the time it double-byte character sets. Because each is loaded into central storage. character requires two bytes, the typing, display, and printing of DBCS characters dynamic link library (DLL). A file containing requires hardware and programs that support executable code and data bound to a program DBCS. Contrast with single-byte character set. at load time or run time. The code and data in a dynamic link library can be shared by several doubleword. A sequence of bits or characters applications simultaneously. that comprises eight bytes (two 4-byte words) and is referenced as a unit. dynamic reconfiguration. The ability to make changes to the channel subsystem and to the downwardly compatible. The ability of operating system while the system is running. applications to run on previous releases of z/OS. dynamic routing protocol. A protocol that adjusts automatically to network topology or drain. Allowing a printer to complete its traffic changes. current work before stopping the device. dynamic VIPA (DVIPA). A function that allows driving system. The system used to install the system to move IP addresses in event of the program. Contrast with target system. an application, TCP/IP stack, or LPAR failure.

DS DB. directory services database. dynamic VPN. A type of virtual private network that requires a separate server to dsname. data set name. support the exchange of the keys that are used to encrypt data at each end point. DSORG. Data set organization (parameter of DCB and DD and in a data class definition).

25 dynamic XCF links. Links using the encapsulation. In communications, a cross-system coupling facility hat can be technique used by layered protocols by which automatically generated any time TCP/IP a layer adds control information to the protocol becomes active within a sysplex. data unit (PDU) from the layer it supports. In this respect, the layer encapsulates the data from the supported layer. In the Internet suite of protocols, for example, a packet would E contain control information from the physical layer, followed by control information from the EB. exabyte. network layer, followed by the application EBCDIC. Extended Binary Coded Decimal protocol data. See data link switching (DLSw). Interchange Code. enclave. A transaction that can span multiple EBN. extended border node. dispatchable units (SRBs and tasks) in one or more address spaces and is reported on and e-business. (1) The transaction of business managed as a unit. over an electronic medium such as the Internet. (2) The transformation of key encrypt. To systematically encode data so business processes through the use of that it cannot be read without knowing the Internet technologies. coding key.

EC. engineering change. end node. See Advanced Peer-to-Peer Networking (APPN) end node. ECSA. extended common service area. endian. An attribute of data representation EDT. eligible device table. that reflects how certain multi-octet data is stored in memory. See big endian, little element. In SMP/E, part of a product, such as endian. a , module, dialog panel, or sample code. enterprise. The composite of all operational entities, functions, and resources that form the eligible device table (EDT). An installation total business concern. defined representation of the devices that are eligible for allocation. The EDT defines the Enterprise Extender. A means for sending esoteric and generic relationship of these SNA data over an IP network. Enterprise devices. During IPL, the installation identifies Extender is an extension of SNA High the EDT that z/OS uses. After IPL, jobs can Performance Routing that provides request device allocation from any of the encapsulation of SNA application traffic within esoteric device groups assigned to the UDP frames. selected EDT. An EDT is identified by a unique ID (two digits), and contains one or more Enterprise Systems Connection (ESCON). esoterics and generics. A set of products and services that provides a dynamically connected environment using EN. end node. optical cables as a transmission medium.

26 Introduction to the New Mainframe: z/OS Basics entry area. In z/OS, the part of a console ESCON Manager (ESCM). A licensed screen where operators can enter commands program that provides host control and or command responses. intersystem communication capability for ESCON Director connectivity operations. See entry name. In assembler language, a ESCON Director. programmer-specified name within a control section that identifies an entry point and can ESCON multiple image facility (EMIF). In be referred to by any control section. See entry mainframe computing, a function that enables point. logical partitions (LPARs) to share an ESCON channel path by providing each LPAR with its entry point. The address or label of the first own channel-subsystem image. instruction that is executed when a routine is entered for execution. Within a load module, esoteric. An installation-defined and named the location to which control is passed when grouping of I/O devices of usually the same the load module is invoked. device group. Eligible device tables (EDTs) define the esoteric and generic relationship of entry point name. The symbol (or name) that these devices. The name you assign to an represents an entry point. See entry point. esoteric is used in the JCL DD statement. The job then allocates a device from that group EOF. End of file. instead of a specific device number or generic device group. Synonymous with esoteric ephemeral port number. In some TCP/IP device group. implementations, a temporary port number assigned to a process for the duration of a call. Ethernet. A packet-based networking Ephemeral port numbers are typically technology for local area networks (LANs) that assigned to client processes that must provide allows multiple access and handles contention servers with a client port number so that the by using Carrier Sense Multiple Access with server can respond to the correct process. Collision Detection (CSMA/CD) as the access method. Ethernet is standardized in the IEEE ER. explicit route. 802.3 specification. ESCON. Enterprise Systems Connection. ETR. External Time Reference. ESCON channel. A channel that supports exabyte. For processor, real and virtual ESCON protocols. storage capacities and channel volume: 1 152 (60) ESCON Director (ESCD). A switch for 921 504 606 846 976 bytes or 2 . ESCON optical channels that provides exception SYSMOD. A SYSMOD that is in connectivity capability and control for the error or that requires special processing attachment of any two links to each other. See before it can be installed. ++HOLD and ESCON Manager. ++RELEASE statements identify exception SYSMODs.

EXCP. execute channel programs.

27 executable. A load module or program object extended remote copy (XRC). A hardware- which has yet to be loaded into memory for and software-based remote copy service execution. option that provides an asynchronous volume copy across storage subsystems for disaster executable program. (1) A program in a form recovery, device migration, and workload suitable for execution by a computer. The migration. program can be an application or a shell script. (2) A program that has been link-edited and external reference. In an object deck, a can therefore be run in a processor. (3) A reference to a symbol, such as an entry point program that can be executed as a name, defined in another program or module. self-contained procedure. It consists of a main program and, optionally, one or more External Time Reference (ETR). Obsolete subprograms. See executable, load module. term for Sysplex Timer®. explicit route. In SNA, a series of one or more transmission groups that connect two subarea nodes. An explicit route is identified F by an origin subarea address, a destination failover. (1) A transparent operation that subarea address, an explicit route number, switches to a redundant or standby system and a reverse explicit route number. Contrast when services fail. (2) A cluster event where with virtual route (VR). the primary database server or application Extended Binary-Coded Decimal server switches over to a backup system due Interchange Code (EBCDIC). An encoding to the failure of the primary server. (3) The scheme that is used to represent character routing of all transactions to a second data in the z/OS environment. Contrast with controller when the first controller fails. ASCII and Unicode. fanout. A single output that becomes input to extended border node (EBN). A border node multiple branches. that interconnects: (a) APPN networks having Fast Ethernet. An Ethernet standard that different network identifiers; or (b) separate provides a data rate of 100 Mbps. partitions of the same APPN network, where the partitioning is to allow isolated topology FDDI. Fiber Distributed Data Interface. subnetworks (or clusters). An extended border node supports intermediate network routing, feature. Part of a product that is either allowing it to support LU-LU sessions that do included with the product or can be ordered not terminate in its native network. Contrast separately. with peripheral border node. feature code. A four-digit code used by IBM to extended MCS console. In z/OS, a console process hardware and software orders. other than an MCS console from which operators or programs can issue system FEP. front-end processor. commands and receive messages. An extended MCS console is defined through an fetch. The dynamic loading of a procedure. OPERPARM segment.

28 Introduction to the New Mainframe: z/OS Basics FFST. First Failure Support Technology. file. A collection of related data that is stored and retrieved by an assigned name. A file can Fiber Connection Environment (FICON®). include information that starts a program An optical fiber communication method (program-file object), contains text or graphics offering channels with high data rate, high (data-file object), or processes a series of bandwidth, increased distance and a large commands (). See data set. number of devices per control unit for mainframe systems. It can work with, or File Transfer Protocol (FTP). In TCP/IP, an replace, ESCON links. application protocol used for transferring files to and from host computers. Fiber Distributed Data Interface. An American National Standards Institute (ANSI) FILEDEF. file definition statement. standard for a 100-Mbps LAN using fiber optic cables. FIN. no more data from sender. fiber link. The physical fiber optic connections firewall. (1) A network configuration, usually and transmission media between optical fiber both hardware and software, that prevents transmitters and receivers. A fiber link can unauthorized traffic into and out of a secure comprise one or more fiber cables and network. (2) An intermediate server that patchports in fiber management cabinets. functions to isolate a secure network from an Each connection in the fiber link is either insecure network. permanent or mutable. First Failure Support Technology (FFST) fiber optic cable. A fiber or bundle of fibers in dump. A dump produced by First Failure a structure built to meet optic, mechanical, and Support Technology, a licensed program that environmental specifications. captures information about a potential problem when it occurs. fibre-channel connection (FICON). A fibre-channel communication protocol first-in-first-out (FIFO). A queuing technique designed for IBM mainframe computers and in which the next item to be retrieved is the peripherals. oldest item in the queue.

FICON. fibre channel connection. fix. A correction of an error in a program, usually a temporary correction or bypass of FID. format identifier. defective code. field-replaceable unit (FRU). An assembly fixed-length record. A record having the that is replaced in its entirety when any one of same length as all other records with which it its components fails. See is logically or physically associated. Contrast customer-replaceable unit. with variable-length record.

FIFO. first-in-first-out. FlashCopy®. A point-in-time copy services function that can quickly copy data from a source location to a target location.

29 FMID. function modification identifier. . A high-level language used primarily for applications involving numeric footprint. (1) The amount of computer storage computations. In previous usage, the name of that is occupied by a computer program. For the language was written in all capital letters, example, if a program occupies a large that is, FORTRAN. amount of storage, it has a large footprint. (2) Amount of floor space occupied by a piece of forward explicit route. Explicit routes equipment. originating in the host. foreground. (1) in multiprogramming, the forwarding. The act of moving a datagram environment in which high-priority programs between two different networks or are executed. (2) Under TSO, the environment subnetworks. in which programs are swapped in and out of central storage to allow CPU time to be shared frame. (1) The hardware support structure, among terminal users. All command processor covers, and all electrical parts mounted there programs execute in the foreground. Contrast that are packaged as one entity for shipping. with background. For a mainframe microprocessor cluster, a frame contains one or two central processor foreground job. (1) A high-priority job, usually complexes (CPCs), support elements, and AC a real-time job. (2) Under TSO, any job power distribution. (2) In networking, the block executing in a swapped region of central of information transmitted between two or storage, such as a command processor or a more stations in the data link layer of a terminal user's program. Contrast with network. It includes delimiters, control background job. characters, information, and checking characters. foreign key. A column or set of columns in a dependent table of a constraint relationship. frame relay. A protocol for routing frames The key must have the same number of through the network based on the address columns, with the same descriptions, as the field (data link connection identifier) in the primary key of the parent table. Each foreign frame and for managing the route or virtual key value must either match a parent key connection. value in the related parent table or be null. FRSN. flow reduction sequence number. fork. To create and start a child process. Forking is similar to creating an address space FRU. field-replaceable unit. and attaching. It creates a copy of the parent process, including open file descriptors. FTP. File Transfer Protocol. format identification field (FID, FID field). In FTPD. FTP daemon. SNA, a field in each transmission header (TH) full screen mode. A form of screen that indicates the format of the TH; that is, the presentation in which the contents of an entire presence or absence of certain fields. TH terminal screen can be displayed at once. formats differ in accordance with the types of Full-screen mode is often used for nodes between which they pass. fill-in-the-blanks prompting.

30 Introduction to the New Mainframe: z/OS Basics full-duplex. See duplex. generalized trace facility (GTF). In a z/OS environment, a service program that records fullword. A sequence of bits or characters that significant system events, such as supervisor comprises four bytes (one word) and is calls and start I/O operations, for the purpose referenced as a unit. of problem determination. Like system trace, GTF gathers information used to determine fullword boundary. A storage location whose and diagnose problems that occur during address is evenly divisible by 4. system operation. Unlike system trace, however, GTF can be tailored to record very function. In SMP/E, a product (such as a specific system and user program events. system component or licensed program) that can be installed in a user's system if desired. generation data group (GDG). A collection of Functions are identified to SMP/E by the historically related non-VSAM data sets that ++FUNCTION statement. Each function must are arranged in chronological order; each data have a unique FMID. set is called a generation data set. function modification identifier (FMID). A generic. A z/OS-defined grouping of devices code that identifies the release levels of a with similar characteristics. For example: the z/OS licensed program. device types 3270-X, 3277-2, 3278-2, -2A, -3, -4, and 3279-2a, -2b, -2c, -3a, -3b belong to the same generic. Every generic has a generic G name that is used for device allocation in the JCL DD statement. z/OS interprets this name gateway. A device or program used to connect as “take any device in that group.” In a given networks or systems with different network z/OS configuration, each eligible device table architectures. The systems may have different (EDT) has the same list of generics. characteristics, such as different communication protocols, different network Geographically Dispersed Parallel architecture, or different security policies, in Sysplex™ (GDPS®). An application that which case the gateway performs a translation integrates Parallel Sysplex technology and role as well as a connection role. remote copy technology to enhance application availability and improve disaster gateway node. A node that is an interface recovery. GDPS topology is a Parallel Sysplex between networks. cluster spread across two sites, with all critical data mirrored between the sites. GDPS Gb. gigabit. manages the remote copy configuration and storage subsystems; automates Parallel GB. gigabyte. Sysplex operational tasks; and automates failure recovery from a single point of control. Gbps. gigabits per second. Gigabit Ethernet. A variation of the Ethernet GDG. generation data group. protocol that is capable of transmitting data at one billion bits per second.

31 gigabyte. In decimal notation, 1 073 741 824 guest. An operating system, such as Linux or bytes when referring to memory capacity; in all z/OS, running in a virtual machine managed other cases, it is defined as 1 000 000 000 by the z/VM® Control Program (CP). bytes. GUI. graphical . global access checking. The ability to allow an installation to establish an in-storage table of default values for authorization levels for selected resources. H global resource serialization. A z/OS half-duplex. In data communication, function that provides a serialization pertaining to transmission in only one direction mechanism for resources (typically data sets) at a time. Contrast with duplex. across multiple z/OS systems. handshake. In Transport Layer Security global resource serialization complex. One (TLS), the initial setup of a TLS connection. or more z/OS systems that use global hardcopy log. In systems with multiple resource serialization to serialize access to console support or a graphic console, a shared resources (such as data sets on permanent record of system activity. shared DASD volumes). hardware. Physical equipment, as opposed to global zone. A group of records in a CSI data the computer program or method of use; for set used to record information about example, mechanical, magnetic, electrical, or SYSMODs received for a particular system. electronic devices. Contrast with software. The global zone also contains information that (1) enables SMP/E to access target and hardware configuration definition (HCD). distribution zones in that system, and (2) An interactive interface in z/OS that is used to enables you to tailor aspects of SMP/E define hardware configurations to the processing. operating system and the channel subsystem. gratuitous ARP. An unsolicited ARP Hardware Management Console (HMC). A response. console used to monitor and control hardware such as the IBM System z9™ processors. Gregorian calendar. The calendar in use since Friday, 15 October 1582 throughout hardware unit. A central processor, storage most of the world. element, channel path, device, and so on. group. A collection of RACF users who can HASP. Houston Automatic Priority. share access authorities for protected resources. HCD. hardware configuration definition.

GTF. generalized trace facility. head of string. The first unit of devices in a string. It contains the string interfaces which connect to controller device interfaces.

32 Introduction to the New Mainframe: z/OS Basics heat sink. A metal base or plate onto which HOLDDATA. In SMP/E, one or more MCSs one or more components are mounted to used to indicate that certain SYSMODs absorb, carry away, or radiate the heat contain errors or require special processing generated by the components. Overheating before they can be installed. ++HOLD and can result in the malfunction or destruction of ++RELEASE statements are used to define the parts generating the heat or might cause HOLDDATA. SYSMODs affected by damage to other parts of the circuit. HOLDDATA are called exception SYSMODs. hexadecimal. A base 16 numbering system. hop. In APPN, a portion of a route that has no Hexadecimal digits range from 0 through 9 intermediate nodes. It consists of only a single (decimal 0 to 9) and uppercase or lowercase A transmission group connecting adjacent through F (decimal 10 to 15) and A through F, nodes. giving values of 0 through 15. host. A computer that is connected to a HFS. hierarchical . network and provides an access point to that network. The host can be a client, a server, or hierarchical file system (HFS) data set. A both a client and server simultaneously. data set that contains a POSIX-compliant hierarchical file system, which is a collection of hot plug. To install a hardware component files and directories organized in a hierarchical without turning off the system. structure, that can be accessed using z/OS UNIX System Services facilities. hot-swap. Pertaining to a device that is capable of being replaced while the system is high-level language (HLL). A programming on. language above the level of assembler language and below that of program Houston Automatic Spooling Priority generators and query languages. Examples (HASP). A computer program that provides are C, C++, COBOL, Fortran, and PL/I. supplementary job management, data management, and task management highly parallel. Refers to multiple systems functions, such as: control of job flow, ordering operating in parallel, each of which can have of tasks, and spooling. See JES2. multiple processors. See n-way. HPR. high performance routing. HiperSockets™. A technology that provides high-speed TCP/IP connectivity within a HTTP. Hypertext Transfer Protocol. central processor complex. It eliminates the need for any physical cabling or external HTTP server. A program that enables a networking connection between servers computer that uses the Hypertext Transfer running in different LPARs. Protocol (HTTP) to serve objects by responding to requests from other programs, HLL. high-level language. such as browsers.

HMC. Hardware Management Console.

33 hub. In a network, a point at which circuits are IBM Support Center. The IBM organization either connected or switched. For example, in responsible for software service. a star network, the hub is the central node; in a star/ring network, it is the location of wiring IBM systems engineer (SE). An IBM service concentrators. representative who performs maintenance services for IBM software in the field.

ICMP. Internet Control Message Protocol. I ICN. interchange network node. I/O. Input/output. ICSF. Integrated Cryptographic Service I/O cage. A physical area of the processor Facility. frame where connections to the central processor complex are made. IDCAMS. An IBM program used to process access method services commands. It can be I/O cluster. A sysplex that owns a managed invoked as a job or jobstep, from a TSO channel path for a logically partitioned terminal, or from within a user's application processor configuration. program.

I/O device. A printer, tape drive, hard disk IDS. intrusion detection services. drive, and so on. Devices are logically grouped inside units, which are in turn grouped into IEEE. Institute of Electrical and Electronic strings. The first unit, known as the head of Engineers. string, contains string interfaces which connect to controller device interfaces and IETF. Internet Engineering Task Force. eventually to processor CHPIDs. Devices are IKE. Internet Key Exchange. represented as lines of text within the appropriate unit object in the configuration image. A single instance of the z/OS diagram. operating system.

IAC. Interpret As Command. IMS. Information Management System.

IBM. International Business Machines IMS DB. Information Management System Corporation. Database Manager.

IBM Security Server. An IBM licensed IMS DB data sharing group. A collection of program that provides access control by one or more concurrent IMS DB subsystems identifying users to the system; verifying users that directly access and change the same data of the system; authorizing access to protected while maintaining data integrity. resources; logging detected, unauthorized attempts to enter the system; and logging independent LU. See SSCP-independent LU. detected accesses to protected resources. Also known as Resource Access Control Facility or RACF.

34 Introduction to the New Mainframe: z/OS Basics Information Management System (IMS). input/output definition file (IODF). A VSAM IBM product that supports hierarchical linear data set that contains I/O definition databases, data communication, translation information, including processor I/O definitions processing, and database backout and and operating system I/O definitions, including recovery. all logical objects and their connectivity in the hardware configuration. initial program load (IPL). The initialization procedure that causes the z/OS operating install. In SMP/E, to apply a SYSMOD to the system to begin operation. During IPL, system target libraries or to accept a SYSMOD into programs are loaded into storage and z/OS is the distribution libraries. made ready to perform work. Synonymous with boot, load. installation . The means by which an IBM software product may be modified by a initial storage allocation. The amount of customer's system programmers to change or central and expanded storage to be assigned extend the functions of the product. to a logical partition. instruction line. In z/OS, the part of the initiator. That part of an operating system that console screen that contains messages about reads and processes operation control console control and input errors. language statements from the system input device. Integrated Services Digital Network (ISDN). An international communications standard for initiator/terminator. The sending voice, video, and data over digital function that selects jobs and job steps to be telephone lines. executed, allocates input/output devices for them, places them under task control, and at interactive problem control system (IPCS). completion of the job, supplies control A component of z/OS that permits online information for writing job output on a system problem management, interactive problem output unit. diagnosis, online debugging for dumps, problem tracking, and problem reporting. input/output. Pertaining to a device, process, channel, or communication path involved in Interactive System Productivity Facility data input, data output, or both. (ISPF). A dialog manager for interactive applications. It provides control and services input/output configuration data set to permit execution of dialogs. (IOCDS). A file that contains different configuration definitions for the selected interactive. Pertaining to a program or system processor. Only one IOCDS is used at a time. that alternately accepts input and responds. In The IOCDS contains I/O configuration data for an interactive system, a constant dialog exists the files associated with the processor between user and system. Contrast with controller on the host processor, as it is used batch. by the channel subsystem. The channel subsystem (CSS) uses the configuration data to control I/O requests. The IOCDS is built from the production IODF.

35 interchange node. (1) A node that acts as IOP. input/output program. both an APPN network node and a type 5 subarea node to transform APPN protocols to IP. Internet Protocol. subarea protocols and vice versa. (2) Contrast with migration data host. IP address. The unique 32-bit address (or, for IP version 6, the 128-bit address) that internal reader. A facility that transfers jobs to specifies the location of each device or JES. workstation in the Internet. For example, 9.67.97.103 is an IP address. The address Internet Control Message Protocol (ICMP). field contains two parts: the first part is the An Internet protocol that is used by a gateway network address; the second part is the host to communicate with a source host, for number. example, to report an error in a datagram. IP layer. Synonym for network layer. Internet Protocol (IP). A protocol that routes data through a network or interconnected IP network. A network that consists of networks. Internet Protocol (IP) acts as an subnetworks that are connected through the intermediary between the higher protocol Internet Protocol. layers and the physical network. IP route. A network path between any two IP Internet. The worldwide collection of addressable points in a network. interconnected networks that use the Internet suite of protocols and permit public access. IP Security Architecture. A collection of Internet Engineering Task Force (IETF) interrupt. A suspension of a process, such as standards that define an architecture at the the execution of a computer program, caused Internet Protocol (IP) layer to protect IP traffic by an event external to that process, and by using various security services. performed in such a way that the process can be resumed. IPA. IP network availability. intranet. A private network that integrates IPCS. Interactive Problem Control System. Internet standards and applications (such as IPL. initial program load. Web browsers) with an organization's existing computer networking infrastructure. IPSec. IP Security. intrusion detection service. Software that IPv4. Internet Protocol version 4. detects attempts or successful attacks on monitored resources that are part of a network IPv6. Internet Protocol Version 6. or host system. IQDIO. Internal Queued Direct I/O. IOCDS. input/output configuration data set. ISC. inter-system coupling. IOCP. input/output configuration program. ISDN. Integrated Services Digital Network. IODF. input/output definition file.

36 Introduction to the New Mainframe: z/OS Basics ISMF. Interactive storage management facility. job class. Any one of a number of job categories that can be defined. With the ISPF. Interactive System Productivity Facility. classification of jobs and direction of initiator/terminators to initiate specific classes ISPF/PDF. Interactive System Productivity of jobs, it is possible to control the mixture of Facility/Program Development Facility. jobs that are performed concurrently.

ITSO. International Technical Support (JCL) statements. Organization. Statements placed into an input stream to define work to be done, methods to be used, IVP. installation verification procedure. and the resources needed.

job control language (JCL). A sequence of J commands used to identify a job to an operating system and to describe a job's JCL. job control language. requirements.

JES. job entry subsystem. job entry subsystem (JES). A system facility for spooling, job queueing, and managing I/O. JES2. A z/OS subsystem that receives jobs into the system, converts them to internal job priority. A value assigned to a job that is format, selects them for execution, processes used as a measure of the job's relative their output, and purges them from the importance while the job contends with other system. In an installation with more than one jobs for system resources. processor, each JES2 processor independently controls its job input, job separator pages. Those pages of printed , and output processing. Contrast output that delimit jobs. with JES3. job step. The job control (JCL) statements JES3. A z/OS subsystem that receives jobs that request and control execution of a into the system, converts them to internal program and that specify the resources format, selects them for execution, processes needed to run the program. The JCL their output, and purges them from the statements for a job step include one EXEC system. In complexes that have several statement, which specifies the program or loosely-coupled processing units, the JES3 procedure to be invoked, followed by one or program manages processors so that the more DD statements, which specify the data global processor exercises centralized control sets or I/O devices that might be needed by over the local processors and distributes jobs the program. to them through a common job queue. Julian date. A date format that contains the Contrast with JES2. year in positions 1 and 2, and the day in job. A unit of work for an operating system. positions 3 through 5. The day is represented Jobs are defined by JCL statements. as 1 through 366, right-adjusted, with zeros in the unused high-order position.

37 jumper cable. Fiber used to make mutable LAN segment. (1) Any portion of a LAN (for connections between patchports. example, a bus or ring) that can operate independently, but that is connected to other parts of the network by means of bridges. (2) A ring or bus network without bridges. K Language Environment. Short form of z/OS Kb. kilobit. Language Environment. A set of architectural constructs and interfaces that provides a KB. kilobyte. common runtime environment and runtime Kbps. Kilobits per second. services for C, C++, COBOL, Fortran, PL/I, VisualAge® PL/I, and Java™ applications kernel. The part of an operating system that compiled by Language performs basic functions such as allocating Environment-conforming compilers. hardware resources. last-in-first-out (LIFO). A queuing technique key ring. In computer security, a file that in which the next item to be retrieved is the contains public keys, private keys, trusted item most recently placed in the queue. roots, and certificates. LCSS. logical channel subsystem. key-sequenced data set (KSDS). A VSAM file or data set whose records are loaded in LCU. logical control unit. ascending key sequence and controlled by an LDAP. Lightweight Directory Access Protocol. index. Records are retrieved and stored by keyed access or by addressed access, and LEN node. low-entry network (LEN) node. new records are inserted in key sequence by means of distributed free space. Relative byte library. A partitioned data set (PDS) that addresses can change because of control contains a related collection of named interval or control area splits. members. See partitioned data set. keyword. A part of a command operand that LIC. Licensed Internal Code. consists of a specific character string (such as DSNAME=). licensed internal code (LIC). Microcode that IBM does not sell as part of a machine, but KSDS. key-sequenced data set. licenses to the customer. LIC is implemented in a part of storage that is not addressable by user programs. Some IBM products use it to implement functions as an alternative to L hard-wired circuitry. LAN. local area network.

38 Introduction to the New Mainframe: z/OS Basics licensed program. A software package that linkage editor. An operating system can be ordered from the program libraries, component that resolves cross-references such as IBM Software Distribution (ISMD). between separately compiled or assembled IMS and CICS are examples of licensed modules and then assigns final addresses to programs. create a single relocatable load module. The linkage editor then stores the load module in a LIFO. last-in-first-out. load library on disk.

Lightweight Directory Access Protocol linked list. A list in which the data elements (LDAP). An Internet protocol standard, based may be dispersed but in which each data on the TCP/IP protocol, which allows the element contains information for locating the access and manipulation of data organized in next. Synonymous with chained list. a Directory Information Tree (DIT). link-edit. To create a loadable computer line switching. Synonym for circuit switching. program by means of a linkage editor or binder. link. In data communications, a transmission medium and data link control component that list structure. A coupling facility structure that together transmit data between adjacent enables multisystem applications in a sysplex nodes. to share information organized as a set of lists or queues. A list structure consists of a set of link layer. See data link layer. lists and an optional lock table, which can be used for serializing resources in the list link library. A data set containing link-edited structure. Each list consists of a queue of list object modules. entries. link pack area (LPA). An area of virtual little endian. A format for storage of binary storage that contains reenterable routines that data in which the least significant byte is are loaded at IPL (initial program load) time placed first. Little endian is used by the Intel® and can be used concurrently by all tasks in hardware architectures. Contrast with big the system. endian. link state. In routing protocols, the advertised LLC. logical link control. information about the usable interfaces and reachable neighbors of a router or network. LMOD. In SMP/E, an abbreviation for load The protocol's topological database is formed module. from the collected link-state advertisements. load balancing. The monitoring and link station. In SNA, a named resource within management of the workload on servers. If an APPN or a subarea node that represents one server exceeds its workload, requests are the connection to another APPN or subarea forwarded to another server with more node that is attached by an APPN or a capacity. subarea link. In the resource hierarchy in a subarea network, the link station is subordinate to the subarea link.

39 load module. An executable program stored logical channel subsystem (LCSS). A in a partitioned data set program library. See channel subsystem structure that provides program object. channel path and subchannel controls for configuring from one to four channel local area network (LAN). A network that subsystem images. Each channel subsystem connects several devices in a limited area image can be configured with up to 256 (such as a single building or campus) and that channel paths, and each logical partition has can be connected to a larger network. access to one channel subsystem image. local system queue area (LSQA). In z/OS, logical control unit (LCU). A single control one or more segments associated with each unit (CU) with or without attached devices, or a virtual storage region that contain job-related group of one or more CUs that share devices. system control blocks. In a channel subsystem (CSS), an LCU represents a set of CUs that physically or local topology database. A database in an logically attach I/O devices in common. APPN or LEN node containing an entry for each transmission group (TG) having at least logical partition (LPAR). A subset of a single one end node for an endpoint. In an end node, system that contains resources (processors, the database has one entry for each TG memory, and input/output devices). A logical connecting to the node. In a network node, the partition operates as an independent system. database has an entry for each TG connecting If hardware requirements are met, multiple the network node to an end node. Each entry logical partitions can exist within a system. describes the current characteristics of the TG See logically partitioned (LPAR) mode. that it represents. A network node has both a local and a network topology database, while logical partitioning. A function of an an end node has only a local topology operating system that enables the creation of database. logical partitions.

Locate search. The means which directory logical subsystem. The logical functions of a services in a node uses to find a resource that storage controller that allow one or more host is not in that node. The Locate search enables I/O interfaces to access a set of devices. The directory services to ask the directory services controller aggregates the devices according to components in other APPN nodes for the addressing mechanisms of the associated information on the target resource. See I/O interfaces. One or more logical broadcast search, directed Locate search. subsystems exist on a storage controller. In general, the controller associates a given set lock structure. A coupling facility structure of devices with only one logical subsystem. that enables applications in a sysplex to implement customized locking protocols for serialization of application-defined resources. The lock structure supports shared, exclusive, and application-defined lock states, as well as generalized contention management and recovery protocols.

40 Introduction to the New Mainframe: z/OS Basics logical unit (LU). An access point through low entry networking (LEN) node. A node which a user or application program accesses that provides a range of end-user services, the SNA network to communicate with another attaches directly to other nodes using peer user or application program. An LU can protocols, and derives network services support at least two sessions—one with an implicitly from an adjacent APPN network SSCP and one with another LU—and may be node, that is, without the direct use of CP-CP capable of supporting many sessions with sessions. other LUs. LP. logical partition. logical unit type 6.2. The SNA logical unit type that supports general communication LPA. link pack area. between programs in a cooperative processing environment. LPAR. logically partitioned (mode). logically partitioned (LPAR) mode. A central LRECL. logical record length. processor complex (CPC) power-on reset LSPR. Large System Performance Reference. mode that enables use of the PR/SM™ feature and allows an operator to allocate CPC LSQA. local system queue area hardware resources (including central processors, central storage, expanded LU. logical unit. storage, and channel paths) among logical partitions. LU-LU session. A logical connection between two logical units (LUs) in an SNA network that logoff. (1) The procedure by which a user typically provides communication between two ends a terminal session. (2) In VTAM, a users. request that a terminal be disconnected from a VTAM application program. logon. (1) The procedure by which a user M begins a terminal session. (2) In VTAM, a request that a terminal be connected to a MAC. media access control (MAC). VTAM application program. MAC address. A standardized data link layer LOGREC. Log recording data set. address required for every port or device that connects to a local-area network (LAN). Other loop. A situation in which an instruction or a devices in the network use these addresses to group of instructions execute repeatedly. locate specific ports in the network and to create and update routing tables and data loosely coupled. A multisystem structure that structures. MAC addresses are 6 bytes long requires a low degree of interaction and and are controlled by the IEEE. cooperation between multiple z/OS images to process a workload. See tightly coupled. machine check interruption. An interruption that occurs as a result of an equipment malfunction or error.

41 machine readable. Pertaining to data a Mb. megabit. machine can acquire or interpret (read) from a storage device, a data medium, or other MB. megabyte. source. Mbps. megabits per second. macro. An instruction in a source language that is to be replaced by a defined sequence of MCS. (1) Multiple console support. (2) instructions in the same source language. Modification control statement (in SMP/E). macro instruction. Obsolete term for macro. MCS console. A non-SNA device defined to z/OS that is locally attached to a z/OS system main task. In the context of z/OS multitasking, and is used to enter commands and receive the main program in a multitasking messages. environment. MDH. migration data host. mainframe. A computer, usually in a computer center, with extensive capabilities media access control (MAC). In LANs, the and resources to which other computers may sublayer of the data link control layer that be connected so that they can share facilities. supports media-dependent functions and uses the services of the physical layer to provide major node. In VTAM, a set of resources that services to the logical link control (LLC) can be activated and deactivated as a group. sublayer. The MAC sublayer includes the See minor node. method of determining when a device has access to the transmission medium. MAS. multi-access spool configuration. megabyte (MB). 220 bytes, 1 048 576 master catalog. A catalog that contains bytes.,048,576 bytes. extensive data set and volume information that VSAM requires to locate data sets, to allocate member. A partition of a partitioned data set and deallocate storage space, to verify the (PDS) or partitioned data set extended authorization of a program or operator to gain (PDSE). access to a data set, and to accumulate usage statistics for data sets. memory dump. Synonymous with dump. master IODF. A centrally kept IODF message processing facility (MPF). A facility containing I/O definitions for several systems used to control message retention, or even for a complete enterprise structure. suppression, and presentation. Master IODFs help to maintain consistent I/O message queue. A queue of messages that data and can provide comprehensive reports. are waiting to be processed or waiting to be master trace. A centralized data tracing sent to a terminal. facility of the master scheduler, used in message text. The part of a message servicing the message processing portions of consisting of the actual information that is z/OS. routed to a user at a terminal or to a program.

42 Introduction to the New Mainframe: z/OS Basics metropolitan area network (MAN). A modem (modulator-demodulator). A device network formed by the interconnection of two that converts digital data from a computer to or more networks which may operate at higher an analog signal that can be transmitted on a speed than those networks, may cross telecommunication line, and converts the administrative boundaries, and may use analog signal received to data for the multiple access methods. Contrast with local computer. area network (LAN) and wide area network (WAN). modification control statement (MCS). An SMP/E control statement used to package a microcode. Stored microinstructions, not SYSMOD. MCSs describe the elements of a available to users, that perform certain program and the relationships that program functions. has with other programs that may be installed on the same system. microprocessor. A processor implemented on one or a small number of chips. modification level. A distribution of all temporary fixes that have been issued since MIF. multiple image facility. the previous modification level. A change in modification level does not add new functions migration data host. A node that acts as both or change the programming support category an APPN end node and a type 5 subarea of the release to which it applies. Contrast with node. Contrast with interchange node. release and version. Whenever a new release of a program is shipped, the modification level migration. Refers to activities, often is set to 0. When the release is reshipped with performed by the system programmer, that the accumulated services changes relate to the installation of a new version or incorporated, the modification level is release of a program to replace an earlier incremented by 1. level. Completion of these activities ensures that the applications and resources on a module. The object that results from system will function correctly at the new level. compiling source code. A module cannot be run. To be run, a module must be bound into a minor node. In VTAM, a uniquely defined program. resource within a major node. Monitor I, II, III. Components of the Resource mixed complex. A global resource Measurement Facility (RMF™). serialization complex in which one or more of the systems in the global resource monoplex. A sysplex consisting of one serialization complex are not part of a system that uses a sysplex couple data set. multisystem sysplex. MPC. multipath channel. MLTG. multilink transmission group. MSU. million service units. See service unit. MNLB. multi-node load balancing. MTU. maximum transmission unit.

43 multi-access spool configuration. Multiple multiprocessor (MP). A CPC that can be systems sharing the JES2 input, job and physically partitioned to form two operating output queues (through a checkpoint data set processor complexes. or coupling facility). multisystem application. An application multicast. (1) Transmission of the same data program that has various functions distributed to a selected group of destinations. (2) A across z/OS images in a multisystem special form of broadcast in which copies of a environment. packet are delivered to only a subset of all possible destinations. (3) Contrast with multisystem console support. Multiple broadcast. console support for more than one system in a sysplex. Multisystem console support allows multiple console support (MCS). The consoles on different systems in the sysplex to operator interface in a z/OS system. communicate with each other (send messages and receive commands) multiple image facility (MIF). A facility that allows multiple logical partitions to share multisystem environment. An environment in ESCON channels (and FICON channels) and which two or more z/OS images reside in one optionally to share any of the control units and or more processors, and programs on one associated I/O devices configured to these image can communicate with programs on the shared channels. The sharing can reduce other images. channel requirements, improve channel utilization, and improve I/O connectivity. multisystem sysplex. A sysplex in which two or more z/OS images are allowed to be Multiple Virtual Storage (MVS). An earlier initialized as part of the sysplex. form of the z/OS operating system. In current usage, the term MVS refers to those services multitasking. Mode of operation that provides and functions of z/OS other than z/OS UNIX for the concurrent, or interleaved, execution of system services, such as those provided by two or more tasks, or threads. Synonymous the base control program (BCP), a base with multithreading. element of z/OS. mutable connection. Connections made with multiplexer channel. A channel designed to fiber jumper cables between patchports in a operate with a number of I/O devices cabinet or between cabinets and active objects simultaneously. Several I/O devices can such as CHPIDs, switches, converters and transfer records at the same time by controllers with ESCON or FICON interfaces. interleaving items of data. Mutable connections are broken when the patchports they connect are not in use. multiprocessing. The simultaneous execution of two or more computer programs MVS. Multiple Virtual Storage. or sequences of instructions. See parallel processing. MVS/ESA. Multiple Virtual Storage/Enterprise Systems Architecture.

44 Introduction to the New Mainframe: z/OS Basics N network ID. (1) In TCP/IP, that part of the IP address that defines a network. (2) A 1- to name server. In the Internet suite of protocols, 8-byte customer-selected name or an 8-byte synonym for domain name server. IBM-registered name that uniquely identifies a specific subnetwork. nanosecond (ns). One billionth of a second; a common measurement of read or write access network interface card (NIC). A printed time to random access memory (RAM). circuit board that plugs into a , server, or workstation. It controls NAU. Network accessible unit. the exchange of data over a network and provides the electronic functions for the data NCP. Network Control Program. link protocol or access method, such as token network. In data communications, a ring or Ethernet. configuration in which two or more locations network job entry (NJE). A JES2 facility that are physically connected for the purpose of provides for the passing of selected jobs, exchanging data. system output data, operator commands, and network accessible unit (NAU). A logical unit messages between communicating job entry (LU), physical unit (PU), control point (CP), or subsystems connected by binary-synchronous system services control point (SSCP). It is the communication lines, channel-to-channel origin or the destination of information adapters, and shared queues. transmitted by the path control network. network layer. In Open Systems network administrator. A person who Interconnection (OSI) architecture, the layer manages the use and maintenance of a that is responsible for routing, switching, and network. link-layer access across the OSI environment. network controller. A concentrator and network node (NN). See Advanced protocol converter used with SDLC links. By Peer-to-Peer Networking (APPN) network converting protocols, which manage the way node. data is sent and received, the IBM 3710 network node server. An APPN network Network Controller allows the use of non-SNA node that provides network services for its devices with an SNA host processor. local LUs and client end nodes. Network File System. A component of z/OS network operator. (1) A person who controls that allows remote access to z/OS host the operation of all or part of a network. (2) In processor data from workstations, personal a multiple-domain network, a person or computers, or any other system on a TCP/IP program responsible for controlling all network that is using client software for the domains. (3) A VTAM application program Network File System protocol. authorized to issue network operator network hardware technician. A person with commands. specific skills and tools for supporting the physical network.

45 network protocol. A communications protocol nonstandard labels. Labels that do not from the network layer of the Open Systems conform to American National Standard or Interconnect (OSI) network architecture, such IBM System/370™ standard label as the Internet Protocol (IP). conventions. network topology database. The NPM. NetView Performance Monitor. representation of the current connectivity between the network nodes within an APPN nucleus initialization program (NIP). The network. It includes: (a) entries for all network stage of z/OS that initializes the control nodes and the transmission groups program; it allows the operator to request last interconnecting them; and (b) entries for all minute changes to certain options specified virtual routing nodes to which network nodes during initialization. are attached. nucleus. That portion of a control program next sequential instruction. The next that always remains in central storage. instruction to be executed in the absence of any branch or transfer of control. null. Empty; having no meaning.

NFS. network file system. n-way. The number (n) of CPs in a CPC. For example, a 6-way CPC contains six CPs. NFTP. NetView® File Transfer.

NHDR. network layer header. O NIC. network interface card. OAF. origin address field. NIP. nucleus initialization program object deck. A module that is the output from NLP. network layer packet. a language translator (such as a compiler or an assembler) and used as input to the linkage NN. network node. editor or binder. An object deck is in relocatable format with machine code that is nonpageable region. In z/OS, a subdivision not executable. Before an object deck can be of the nonpageable dynamic area that is executed, it must be processed by the link-edit allocated to a job step or system task that is utility. Also called object code or simply OBJ. not to be paged during execution. In a nonpageable region, each virtual address is offline. Pertaining to equipment or devices not identical to its real address. Synonymous with under control of the processor. V=R region. offset. The number of measuring units from nonreentrant. A type of program that cannot an arbitrary starting point in a record, area, or be shared by multiple users. control block, to some other point.

OLTP. online transaction processing.

OLU. originating logical unit.

46 Introduction to the New Mainframe: z/OS Basics OMPROUTE server. The routing daemon on operator commands. Statements that system z/OS capable of handling both OSPF and RIP operators an use to get information, alter interfaces concurrently. operations, initiate new operations, or end operations. online. Pertaining to a user's ability to interact with a computer. operator message. A message from an operating system directing the operator to Open Shortest Path First (OSPF). In the perform a specific function, such as mounting Internet suite of protocols, a function that a tape reel; or informing the operator of provides intradomain information transfer. An specific conditions within the system, such as alternative to the Routing Information Protocol an error condition. (RIP), OSPF allows the lowest-cost routing and handles routing in large regional or ORB. operation request block. corporate networks. OS/390. An earlier form of the z/OS operating Open Systems Adapter (OSA). An integrated system. IBM mainframe hardware feature that combines the functions of an I/O channel with OSA. Open Systems Adapter. the functions of a network port to provide direct connectivity between mainframe oscillator. A circuit within a computer that applications and their clients on the attached creates a series of pulses that pace the network. computer's electronic system. The oscillator clock synchronizes, paces and coordinates the Open Systems Interconnection (OSI). The operations of the computer's circuit. interconnection of open systems in accordance with standards of the International OSI. Open Systems Interconnection. Organization for Standardization (ISO) for the OSN. OSA for NCP. exchange of information. OSPF. Open Shortest Path First. OpenSSH. Open Secure Shell. output group. A set of a job's output data sets operating system. Software that controls the that share output characteristics, such as running of programs; in addition, an operating class, destination, and external writer. system may provide services such as resource allocation, scheduling, I/O control, output writer. A part of the job scheduler that and data management. Although operating transcribes specified output data sets onto a systems are predominantly software, partial system output device independently of the hardware implementations are possible. program that produced the data sets. operations log. In z/OS, the operations log is overlay. To write over existing data in storage. a central record of communications and system problems for each system in a sysplex.

P

47 packet. In data communication, a sequence of parallel channel. A channel having a binary digits, including data and control System/360™ and System/370 signals, that is transmitted and switched as a channel-to-control-unit I/O interface that uses composite whole. See frame. bus-and-tag cables as a transmission medium. Contrast with ESCON channel. packet mode operation. See packet switching. parallel OEMI. A reference to an older IBM standard for a computer peripheral interface, packet switching. (1) The process of routing which defines the IBM System/360 and and transferring data by means of addressed System/370 channel to control unit interface. packets so that a channel is occupied only This interface uses ESA/390 logical protocols during transmission of a packet. On over a common bus that configures attached completion of the transmission, the channel is units in a multi-drop bus topology. made available for transfer of other packets. (2) Synonymous with packet mode operation. parallel processing. The simultaneous See circuit switching. processing of units of work by many servers. The units of work can be either transactions or page. (1) In virtual storage systems, a subdivisions of large units of work (batch). See fixed-length block of instructions, data, or both, highly parallel. that can be transferred between central storage and external page storage. (2) To Parallel Sysplex. A sysplex that uses one or transfer instructions, data, or both, between more coupling facilities. central storage and external page storage. parameter. A value or reference passed to a page fault. In z/OS, a program interruption function, command, or program that serves as that occurs when a page that is marked “not in input or controls actions. The value is supplied central storage” is referred to by an active by a user or by another program or process. page. Synonymous with parm. pageable region. In z/OS, a subdivision of the parmlib. All the members in the pageable dynamic area that is allocated to a SYS1.PARMLIB data set that contain job step or a system task that can be paged parameters setting the limits and controlling during execution. Synonymous with V=V the behavior of z/OS. region. parmlib member. A member in the paging. In z/OS, the process of transferring SYS1.PARMLIB data set. pages between central storage and external page storage. partially qualified data set name. A data set name in which the qualifiers are not spelled paging device. In z/OS, a direct access out. Asterisks and percent signs are used in storage device on which pages are stored. place of the undefined qualifiers.

partitionable CPC. A CPC that can be divided into two independent CPCs. See physical partition, single-image mode, side.

48 Introduction to the New Mainframe: z/OS Basics partitioned data set (PDS). A data set in PCHID. physical channel identifier. direct access storage that is divided into partitions, called members, each of which can PCOM. IBM Personal Communications. contain a program, part of a program, or data. Synonymous with program library. Contrast PE. See program error PTF. with sequential data set. peer network. A network in which every partitioned data set extended (PDSE). A resource is self-contained and controls its own system-managed data set that contains an resources. indexed directory and members that are peer-to-peer remote copy (PPRC). Direct similar to the directory and members of connection between DASD controller partitioned data sets. A PDSE can be used subsystems that is used primarily to provide a instead of a partitioned data set. hot standby capability. These connections can partitioning. The process of forming multiple be point-to-point from one DASD controller to configurations from one configuration. another, or they can pass through switches, just as connections from CHPIDs to control password. A unique string of characters units can. known to a computer system and to a user, who must specify the character string to gain percolate. The action taken by the condition access to a system and to the information manager when the returned value from a stored within it. condition handler indicates that the handler could not handle the condition, and the panel. A hardware assembly of port condition will be transferred to the next locations in a communications system. In a handler. network, a patch panel interconnects computers within a local area network (LAN) performance administration. The process of for connection to the Internet or a wide area defining and adjusting workload management network (WAN). A patch panel uses a cable goals and resource groups based on called a patch cord to create each installation business objectives. interconnection. peripheral border node. A border node that patchport. A pair of fibre adapters or interconnects adjacent APPN networks having couplers. Any number of patchports can different network identifiers in order to support participate in a fiber link. To determine the total LU-LU sessions that have one partner LU in its number of patchports in a cabinet, you must native network. Contrast with extended border add the number of patchports of each defined node. panel of the cabinet. peripheral device. The equipment that can path information unit (PIU). A message unit communicate directly with a particular consisting of a transmission header (TH) processing unit. alone, or a TH followed by a basic information unit (BIU) or a BIU segment.

PC. personal computer.

49 peripheral node. A node that uses local physical layer. In the Open Systems addresses for routing and therefore is not Interconnection reference model, the layer that affected by changes in network addresses. A provides the mechanical, electrical, functional, peripheral node requires boundary-function and procedural means to establish, maintain, assistance from an adjacent subarea node. A and release physical connections over the peripheral node can be a type 1, 2.0, or 2.1 transmission medium. node connected to a subarea boundary node. physical partition. Part of a CPC that peripheral subnetwork boundary. A operates as a CPC in its own right, with its connection over a subnetwork boundary own copy of the operating system. between a border and a network node with no border node function. physical unit (PU). In SNA, one of three types of network addressable units. A physical unit permanent connection. Permanent exists in each node of an SNA network to connections are usually made between manage and monitor the resources (such as cabinets with fiber trunk cables. Patchports attached links and adjacent link stations) of a that are permanently connected remain so node, as requested by a system services even when they are not in use. control point logical unit (SSCP-LU) session. permanent data set. A user-named data set physically partitioned (PP) mode. The state that is normally retained for longer than the of a processor complex when its hardware duration of a job or interactive session. units are divided into two separate operating Contrast with temporary data set. configurations or sides. The A-side of the processor controller controls side 0; the B-side PFK. program function key. of the processor controller controls side 1. Contrast with single-image (SI) configuration. PFK capability. On a display console, indicates that program function keys are PIN. personal identification number. supported and were specified at system generation. PIU. path information unit. physical channel ID (PCHID). A number PL/I. A general purpose scientific/business assigned by the machine to a physical channel high-level language. PL/I is a powerful location. procedure-oriented language especially well suited for solving complex scientific problems physical channel identifier (PCHID). The or running lengthy and complicated business physical address of a channel path in the transactions and record-keeping applications. hardware. Logical CHPIDs have corresponding physical channels. Real I/O platform. The operating system environment hardware is attached to a processor through in which a program runs. physical channels. Channels have a physical channel identifier (PCHID) which determines PLPA. pageable link pack area. the physical location of a channel in the processor. The PCHID is a three hexadecimal PLU. primary logical unit. digit number and is assigned by the processor.

50 Introduction to the New Mainframe: z/OS Basics point of presence. A system that has been power-on reset. A key sequence that restarts identified as a contact point for another the operating system (or other program) subnetwork for the purposes of collecting without turning off the electrical power of the topology information. system. pointer. An address or other indication of PPRC. peer-to-peer remote copy. location. PPT. program properties table. point-to-multipoint network. A network in which there are many hosts directly attached preprocessor. A routine that examines within the scope of a single network ID. application source code for preprocessor statements that are then executed, resulting in point-to-point network. Pertaining to data the alteration of the source. transmission between two locations without the use of any intermediate display station or preventive service. (1) The mass installation computer. of PTFs to avoid rediscoveries of the APARs fixed by those PTFs. (2) The SYSMODs policy. A set of rules that are applied to delivered on the program update tape. managed resources. preventive service planning (PSP). port. An access point for data entry or exit. Installation recommendations and HOLDDATA for a product or a service level. PSP port number. The part of a socket address information can be obtained from the IBM that identifies a port within a host. Support Center. portability. The ability to transfer an primary key. One or more characters within a application from one platform to another with data record used to identify the data record or relatively few changes to the source code. control its use. A primary key must be unique.

Portable Operating System Interface printer. A device that writes output data from a (POSIX). Portable Operating System Interface system on paper or other media. for computing environments, an interface standard governed by the IEEE and based on Problem Management. Problem UNIX. POSIX is not a product. Rather, it is an Management investigates the underlying evolving family of standards describing a wide cause of incidents with the aim of preventing spectrum of operating system components incidents of a similar nature from recurring. By ranging from C language and shell interfaces removing errors, which often requires a to system administration. structural change to the IT infrastructure in an organization, the numbers of incidents are PoS. point-of-sale. reduced over time.

POSIX. Portable Operating System Interface.

51 procedure. A set of self-contained high-level program error PTF (PE-PTF). A PTF that has language (HLL) statements that performs a been found to contain an error. A PE-PTF is particular task and returns to the caller. identified on a ++HOLD ERROR statement, Individual languages have different names for along with the APAR that first reported the this concept of a procedure. In C, a procedure error. is called a function. In COBOL, a procedure is a paragraph or section that can only be program fetch. A program that prepares performed from within the program. In PL/I, a programs for execution by loading them at procedure is a named block of code that can specific storage locations and readjusting be invoked externally, usually through a a call. each relocatable address constant. processor. The physical processor, or program function key (PFK). A key on the machine, has a serial number, a set of keyboard of a display device that passes a channels, and a logical processor associated signal to a program to call for a particular with it. The logical processor has a number of program operation. channel path IDs, or CHPIDs, which are the logical equivalent of channels. The logical program interruption. The interruption of the processor may be divided into a number of execution of a program due to some event logical partitions. such as an operation exception, an exponent-overflow exception, or an addressing processor controller. Hardware that provides exception. support and diagnostic functions for the central processors. program level. The modification level, release, version, and fix level. Processor Resource/Systems Manager™ (PR/SM). The feature that allows the program library. A partitioned data set or processor to use several z/OS images PDSE that always contains named members. simultaneously and provides logical program management. The task of preparing partitioning capability. See LPAR. programs for execution, storing the programs, processor storage. Synonymous with central load modules, or program objects in program storage. libraries, and executing them on the operating system. production system. A system where application programs that are already program mask. In bits 20 through 23 of the developed and tested run on a regular basis. program status word (PSW), a 4-bit structure that controls whether each of the fixed-point profile. Data that describes the significant overflow, decimal overflow, exponent-overflow, characteristics of a user, a group of users, or and significance exceptions should cause a one or more computer resources. program interruption. The bits of the program mask can be manipulated to enable or disable the occurrence of a program interruption.

52 Introduction to the New Mainframe: z/OS Basics program module. The output of the binder. A PSS. process scheduling services. collective term for program object and load module. PSW. program status word. program number. The seven-digit code (in PTF. program temporary fix. the format xxxx-xxx) used by IBM to identify each licensed program. PU. physical unit. program object. All or part of a computer PUT. program update tape. program in a form suitable for loading into virtual storage for execution. Program objects are stored in PDSE program libraries and have Q fewer restrictions than load modules. Program objects are produced by the binder. QDIO. queued direct I/O. program status word (PSW). A 64-bit QSAM. queued sequential access method. structure in central storage used to control the order in which instructions are executed, and qualified name. A data set name consisting of to hold and indicate the status of the a string of names separated by periods; for computing system in relation to a particular example, “TREE.FRUIT.APPLE” is a qualified program. See program mask. name. program temporary fix (PTF). A temporary qualifier. A modifier in a qualified name other solution or bypass of a problem diagnosed by than the rightmost name. For example, IBM as resulting from a defect in a current “TREE” and “FRUIT” are qualifiers in unaltered release of the program. “TREE.FRUIT.APPLE.” protocol. The meaning of, and the queue. A line or list formed by items in a sequencing rules for, requests and responses system waiting for processing. used for managing a network, transferring data, and synchronizing the states of network queued direct I/O (QDIO). A hardware components. channel architecture for direct data exchange with I/O devices, where both the I/O device protocol stack. A set of network protocol and the program running on the server layers and software that work together to reference main storage directly through a set process the protocols. of data queues. The QDIO architecture is used by Open Systems Adapter-Express protocol suite. A set of protocols that (OSA-Express), HiperSockets, and Fiber cooperate to handle the transmission tasks for Channel Protocol (FCP) channels. a communication system.

PSH. push data function.

PSP. preventive service planning.

53 queued sequential access method (QSAM). RECEIVE command. The SMP/E command An extended version of the basic sequential used to read in SYSMODs and other data from access method (BSAM). Input data blocks SMPPTFIN and SMPHOLD. awaiting processing or output data blocks awaiting transfer to auxiliary storage are RECEIVE processing. An SMP/E process queued on the system to minimize delays in necessary to install new product libraries. I/O operations. During this process, the code, organized as unloaded partition data sets, is loaded into temporary SMPTLIB data sets. SMP/E RECEIVE processing automatically allocates R the temporary partitioned data sets that correspond to the files on the tape, and loads RACF. Resource Access Control Facility. them from the tape. raised floor. Total area of controlled-access RECFM. record format. space devoted to a company's computing equipment. This space usually includes record. (1) A group of related data, words, or cooling units, electrical panels, fire fields treated as a unit, such as one name, suppression equipment, and other support address, and telephone number. record. (2) A equipment. self-contained collection of information about a single object. A record is made up of a number RAS. reliability, availability, serviceability. of distinct items, called fields. A number of shell programs (for example, awk, join, and RDW. record descriptor word. sort) are designed to process data consisting read access. Permission to read information. of records separated by newlines, where each record contains a number of fields separated reader. A program that reads jobs from an by spaces or some other character. awk can input device or data base file and places them also handle records separated by characters on the job queue. other than newlines. See fixed-length record, variable-length record. real address. In virtual storage systems, the address of a location in central storage. record data. Data sets with a record-oriented structure that are accessed record by record. real storage. Synonymous with central This data set structure is typical of data sets storage. on z/OS and other mainframe operating systems. Contrast with byte stream. reason code. A return code that describes the reason for the failure or partial success of an recording format. For a tape volume, the attempted operation. format of the data on the tape, for example, 18, 36, 128, or 256 tracks. receive. In SMP/E, to read SYSMODs and other data from SMPPTFIN and SMPHOLD recoverability. The extent to which the and store them on the global zone for system can be restored to an operational subsequent SMP/E processing. This is done condition after a system failure. with the RECEIVE command.

54 Introduction to the New Mainframe: z/OS Basics recovery. The process of rebuilding data after refreshable. The reusability attribute that it has been damaged or destroyed, often by allows a program to be replaced (refreshed) restoring a backup version of the data or by with a new copy without affecting its operation. reapplying transactions recorded in a log. A refreshable module cannot be modified by itself or any other module during execution. recovery system. A system that is used in See reusability. place of a primary application system that is no longer available for use. Data from the register. An internal computer component application system must be available for use capable of storing a specified amount of data on the recovery system. This is usually and accepting or transferring this data rapidly. accomplished through backup and recovery techniques, or through various DASD copying register save area (RSA). Area of main techniques, such as remote copy. storage in which contents of registers are saved. recursive routine. A routine that can call itself or be called by another routine that it has related installation materials (RIMs). In IBM called. custom-built offerings, task-oriented documentation, jobs, sample exit routines, redundancy. The use of several identical procedures, parameters, and examples functional units, such as several disk drives or developed by IBM. power supply systems, within one computer system in order to provide data security and a release. A distribution of a new product or new certain degree of fault tolerance in case of function and APAR fixes for an existing hardware failures. product. Contrast with modification level and version. redundant array of independent disk (RAID). A disk subsystem architecture that reliability. A measurement of the ability of a combines two or more physical disk storage system to continue processing without failure. devices into a single logical device to achieve data redundancy. remote copy. A storage-based disaster recovery and workload migration function that reenterable. The reusability attribute that can copy data in real time to a remote location. allows a program to be used concurrently by Two options of remote copy are available. See more than one task. A reenterable module can peer-to-peer remote copy and extended modify its own data or other shared resources, remote copy. if appropriate serialization is in place to prevent interference between using tasks. See remote job entry (RJE). Submission of job reusability. reentrant. control statements and data from a remote terminal, causing the jobs described to be reentrant. The attribute of a routine or scheduled and executed as though application that allows more than one user to encountered in the input stream. share a single copy of a load module. remote operations. Operation of remote sites from a host system.

55 request for comment (RFC). In Internet resource recovery services (RRS). The communications, a document that describes a z/OS system component that provides the part of the Internet suite of protocols and services that a resource manager uses to related experiments. All Internet standards are protect resources. RRS is the z/OS system documented as RFCs. level syncpoint manager. request header (RH). The control information response unit (RU). A message unit that that precedes a request unit (RU). acknowledges a request unit. It may contain prefix information received in a request unit. If request unit (RU). A message unit that positive, the response unit may contain contains control information, end-user data, or additional information (such as session both. parameters in response to BIND SESSION). If negative, the response unit contains sense reserved storage allocation. The amount of data defining the exception condition. central and expanded storage that you can dynamically configure online or offline to a restore. In SMP/E, to remove applied logical partition. SYSMODs from the target libraries by use of the RESTORE command. residency mode (RMODE). The attribute of a program module that specifies whether the RESTORE command. The SMP/E command module, when loaded, must reside below the used to remove applied SYSMODs from the 16MB virtual storage line or may reside target libraries. anywhere in virtual storage. restructured extended executor (REXX). A resolver. In TCP/IP, a program or general-purpose, procedural language for that obtains information from a domain name end-user personal programming, designed for server or a local table for use by an application ease by both casual general users and program. computer professionals. It is also useful for application macros. REXX includes the Resource Access Control Facility (RACF). capability of issuing commands to the An IBM security manager product that underlying operating system from these provides for access control by identifying and macros and procedures. verifying the users to the system, authorizing access to protected resources, logging the resynchronization. A track image copy from detected unauthorized attempts to enter the the primary volume to the secondary volume system and logging the detected accesses to of only the tracks which have changed since protected resources. See IBM Security Server. the volume was last in duplex mode.

Resource Management Facility (RMF). IBM return code. A code produced by a routine to software product that measures and reports indicate its success or failure. It may be used on the performance and availability of a to influence the execution of succeeding system. instructions or programs.

56 Introduction to the New Mainframe: z/OS Basics reusability. The attribute of a module or routine. (1) A program or sequence of section that indicates the extent to which it can instructions called by a program. Typically, a be reused or shared by multiple tasks within routine has a general purpose and is the address space. See refreshable, frequently used. CICS and programming reenterable, serially reusable. languages use routines. (2) A database object that encapsulates procedural logic and SQL reverse explicit route. Explicit routes that statements, is stored on the database server, terminate in the host and must use the same and can be invoked from an SQL statement or set of subarea nodes and transmission groups by using the CALL statement. The three main as their corresponding forward explicit route. classes of routines are procedures, functions, and methods. (3) In REXX, a series of RFC. request for comment. instructions called with the CALL instruction or as a function. A routine can be either internal RH. request/response header. or external to a user's program. (4) A set of RIM. related installation material. statements in a program that causes the system to perform an operation or a series of RIP. Routing Information Protocol. related operations.

RJE. remote job entry. routing code. A code assigned to an operator message and used to route the message to RMF. Resource Measurement Facility. the proper console.

RMODE. residency mode. Routing Information Protocol (RIP). In the Internet suite of protocols, a protocol used to rollback. The process of restoring data exchange intradomain routing information and changed by an application to the state at its to determine optimum routes between internet last commit point. hosts. This protocol determines optimum routes on the basis of route metrics, not link route selection services (RSS). A transmission speed. subcomponent of the topology and routing services component that determines the routing protocol. A technique used by a preferred route between a specified pair of router to find other routers and to remain up to nodes for a given class of service. date about the best way to get to reachable networks. router. A computer that determines the path of network traffic flow. The path selection is made routing table. A collection of routes used to from several paths based on information direct datagram forwarding or to establish a obtained from specific protocols, algorithms connection. The information is passed among that attempt to identify the shortest or best routers to identify network topology and path, and other criteria such as metrics or destination feasibility. protocol-specific destination addresses. routing. The assignment of the communications path by which a message is to reach its destination.

57 RRI. request/response indicator. scan attack. An attack in which a host on the network is trying to determine what ports are RSA. register save area. open on the target host. The host doing the scan may later be the same host that does a RSN. resource sequence number. more virulent attack.

RST. reset the connection. SDLC. synchronous data link control.

RTP. rapid transport protocol. SDSF. System Display and Search Facility.

RTT. round trip time. SDUMP macro. A z/OS macro that can be invoked by authorized programs to take a fast RU. request/response unit. unformatted dump of virtual storage to a data run. To cause a program, utility, or other set. machine function to be performed. SE. Support Element. runtime. Any instant at which a program is Secure Sockets Layer (SSL). A security being executed. Synonymous with execution protocol that provides communication privacy. time. With SSL, client/server applications can runtime environment. A set of resources that communicate in a way that is designed to are used to support the execution of a prevent eavesdropping, tampering, and program. Synonymous with execution message forgery. environment. security administrator. A programmer who manages, protects, and controls access to sensitive information. S sendmail. The mail server that uses the SAF. system authorization facility. Simple Mail Transfer Protocol (SMTP) to route mail from one host to another on the network. SAP. (1) System Assistance Processor. (2) service access point. sense code. A diagnostic code that helps in problem determination. SATF. shared access transport facility. sequential data set. (1) A data set whose save area. Area of main storage in which records are organized on the basis of their contents of registers are saved. successive physical positions, such as on magnetic tape. Contrast with direct data set. scalability. The ability of a system to expand (2) A data set in which the contents are as resources, such as processors, memory, or arranged in successive physical order and are storage, are added. stored as an entity. The data set can contain data, text, a program, or part of a program. Contrast with partitioned data set (PDS).

58 Introduction to the New Mainframe: z/OS Basics serially reusable. The reusability attribute service level. The FMID, RMID, and UMID that allows a program to be executed by more values for an element. The service level than one task in sequence. A serially reusable identifies the owner of the element, the last module cannot be entered by a new task until SYSMOD to replace the element, and all the the previous task has exited. See reusability. SYSMODs that have updated the element since it was last replaced. server. (1) In a network, hardware or software that provides facilities to clients. Examples of a service level agreement (SLA). A written server are a file server, a printer server, or a agreement of the information systems (IS) mail server. (2) A computer that contains service to be provided to the users of a programs, data, or provides the facilities that computing installation. other computers on the network can access. (3) The party that receives remote procedure service provider. (1) In the OSI reference calls. Contrast with client. model, a layer that provides services to the next higher layer. (2) Any company that server address space. Any address space provides services for a fee to its customers, that does work on behalf of a transaction such as telecommunication companies, manager or a resource manager. For example, application service providers, enterprise IT, a server address space could be a CICS AOR, and Internet service providers. or an IMS control region. service processor. The part of a processor service. PTFs and APAR fixes. complex that provides for the maintenance of the complex. service access point (SAP). (1) In Open Systems Interconnection (OSI) architecture, service request block (SRB). In z/OS, a the point at which the services of a layer are dispatchable unit. See dispatch. provided by an entity of that layer to an entity of the next higher layer. (2) A logical point service unit. The amount of service made available by an adapter where consumed by a work request as calculated by information can be received and transmitted. A service definition coefficients and CPU, SRB, single service access point can have many I/O, and storage service units. links terminating in it. (3) A logical address that allows a system to route data between a remote device and the appropriate communications support. (4) The identification of the services provided by a specific communication service provider to one of its users. For example, the Internet Protocol (IP) uses the services of a token-ring adapter. The service access point, in this case, is the name by which IP knows the adapter that is the token-ring address.

59 session. (1) The period of time during which a shared storage. An area of storage that is the user of a terminal can communicate with an same for each virtual address space. Because interactive system; usually, the elapsed time it is the same space for all users, information from when a terminal is logged on to the stored there can be shared and does not have system until it is logged off the system. (2) The to be loaded in the user region. period of time during which programs or devices can communicate with each other. (3) shell. A program that interprets sequences of A logical connection between two network text input as commands. It may operate on an accessible units (NAUs) that can be activated, input stream, or it may interactively prompt and tailored to provide various protocols, and read commands from a terminal. deactivated, as requested. Each session is uniquely identified in a transmission header side. One of the configurations formed by (TH) accompanying any transmissions physical partitioning. exchanged during the session. (2) A logical or SIGA. signal adapter. virtual connection between two stations, programs, or devices on a network that allows SIGP. signal processor. the two elements to communicate and exchange data, or the activities that occur simultaneous peripheral operations online during the establishment, maintenance, and (spool). The reading and writing of input and release of the connection. A session can be output streams on auxiliary storage devices, activated and deactivated as requested. See concurrently while a job is running, in a format transaction. convenient for later processing or output operations. session activation request. In SNA, a request that activates a session between two single point of control. The characteristic a network accessible units (NAUs) and specifies sysplex displays when you can accomplish a session parameters that control various given set of tasks from a single workstation, protocols during session activity; for example, even if you need multiple IBM and vendor BIND and ACTPU. products to accomplish that particular set of tasks. severity code. A part of operator messages that indicates the severity of the error condition single system image. The characteristic a (I, E, or S). product displays when multiple images of the product can be viewed and managed as one sftp. secure FTP. image. shared DASD option. An option that enables single-image (SI) mode. A mode of operation independently operating computing systems to for a multiprocessor (MP) system that allows it jointly use common data residing on shared to function as one CPC. By definition, a direct access storage devices. uniprocessor (UP) operates in single-image mode. Contrast with physically partitioned (PP) configuration.

60 Introduction to the New Mainframe: z/OS Basics single-processor complex. A processing SNA network interconnection (SNI). The environment in which only one processor connection, by gateways, of two or more (computer) accesses the spool and comprises independent SNA networks to allow the entire node. communication between logical units in those networks. The individual SNA networks retain single-system sysplex. A sysplex in which their independence. only one z/OS system is allowed to be initialized as part of the sysplex. In a SNASw. SNA Switching Services. single-system sysplex, XCF provides XCF services on the system but does not provide SNI. SNA network interconnection. signalling services between z/OS systems. See multisystem sysplex. SNMP. Simple Network Management Protocol. SLA. service level agreement. socket. A unique host identifier created by the SLU. secondary logical unit. concatenation of a port identifier with a TCP/IP address. small computer system interface (SCSI). A standard hardware interface that enables a software. (1) All or part of the programs, variety of peripheral devices to communicate procedures, rules, and associated with one another. documentation of a data processing system. (2) A set of programs, procedures, and, SMF. system management facilities. possibly, associated documentation concerned with the operation of a data SMP/E. System Modification processing system. For example, compilers, Program/Extended. library routines, manuals, circuit diagrams. Contrast with hardware. SMPCSI. The SMP/E data set that contains information about the structure of a user's sort/merge program. A processing program system as well as information needed to install that can be used to sort or merge records in a the operating system on a user's system. The prescribed sequence. SMPCSI DD statement refers specifically to the CSI that contains the global zone. This is source code. The input to a compiler or also called the master CSI. assembler, written in a source language.

SMS. Storage Management Subsystem. source program. A set of instructions written in a programming language that must be SMTP. Simple Mail Transfer Protocol. translated to machine language before the program can be run. SNA. Systems Network Architecture. spin data set. A data set that is deallocated (available for printing) when it is closed. Spin off data set support is provided for output data sets just prior to the termination of the job that created the data set.

61 spoofing. For data links, a technique in which SSCP-independent LU. An LU that is able to a protocol initiated from an end station is activate an LU-LU session (that is, send a acknowledged and processed by an BIND request) without assistance from an intermediate node on behalf of the final SSCP. It does not have an SSCP-LU session. destination. In IBM 6611 data link switching, Currently, only an LU 6.2 can be an for example, SNA frames are encapsulated independent LU. into TCP/IP packets for transport across a non-SNA wide area network, unpacked by SSCP-LU session. In SNA, a session another IBM 6611, and passed to the final between a system services control point destination. A benefit of spoofing is the (SSCP) and a logical unit (LU). The session prevention of end-to-end session time-outs. enables the LU to request the SSCP to help initiate LU-LU sessions. spool. simultaneous peripheral operations online. SSCP-SSCP session. In SNA, a session between the system services control point spooled data set. A data set written on an (SSCP) in one domain and the SSCP in auxiliary storage device and managed by JES. another domain. An SSCP-SSCP session is used to initiate and terminate cross-domain spooling. The reading and writing of input and LU-LU sessions. output streams on auxiliary storage devices, concurrently with job execution, in a format SSH. Secure Shell. convenient for later processing or output operations. SSID. subsystem identifier.

SPUFI. SQL Processing Using File Input. SSL. Secure Socket Layer.

SQA. system queue area. stand-alone dump. A kind of dump produced by an operator using a stand-alone dump SQL. Structured Query Language. program, a special program that can run by itself when an operating system is disabled. SREL. system release identifier. star topology. In network architecture, a SRM. system resources manager. network topology in which every node on the network is connected to a central node or SSCH. start subchannel. “hub,” through which they communicate with each other. SSCP. system services control point. start option. In VTAM, a user-specified or SSCP-dependent LU. An LU that requires IBM-supplied option that determines certain assistance from a system services control conditions that are to exist during the time a point (SSCP) in order to initiate an LU-LU VTAM system is operating. Start options can session. It requires an SSCP-LU session. be predefined or specified when VTAM is started.

62 Introduction to the New Mainframe: z/OS Basics started task. In z/OS, an address space that storage group. A collection of storage runs unattended as the result of a START volumes and attributes, defined the storage command. Started tasks are generally used administrator. The collections can be a group for critical applications. The UNIX equivalent is of DASD volume or tape volumes, or a group a daemon. of DASD, optical, or tape volumes treated as single object storage hierarchy. state-oriented protocol. A characteristic of the OSPF protocol, in which interfaces and storage management. The activities of data neighboring routers are always classified as set allocation, placement, monitoring, being in a particular state. Events on the migration, backup, recall, recovery, and network causes these states to change in a deletion. These can be done either manually pre-determined way, providing a predictability or by using automated processes. The and control to the OSPF routers on the Storage Management Subsystem automates network. these processes for you, while optimizing storage resources. See storage management static routing. A method of setting paths subsystem. between hosts, networks, or both, by manually entering routes into the routing table. Static storage management subsystem (SMS). A routes are not affected by routing daemons facility used to automate and centralize the and must be updated manually. management of storage. Using SMS, a storage administrator describes data status-display console. An MCS console allocation characteristics, performance and that can receive displays of system status but availability goals, backup and retention from which an operator cannot enter requirements, and storage requirements to the commands. system through data class, storage class, management class, storage group, and ACS step restart. A restart that begins at the routine definitions. See storage management. beginning of a job step. The restart may be automatic or deferred, where deferral involves string. A collection of one or more I/O devices. resubmitting the job. Contrast with checkpoint The term usually refers to a physical string of restart. units, but may mean a collection of I/O devices which are integrated into a control unit. STI. self-timed interface. structure. A construct used by z/OS to map storage administrator. A person in the data and manage storage on a Coupling Facility. processing center who is responsible for See cache structure, list structure, lock defining, implementing, and maintaining structure. storage management policies. stub area. In the OSPF protocol, a routing storage class. A collection of storage area for which packets can flow into and out of, attributes that identify performance goals and but not through. availability requirements, defined by the storage administrator, used to select a device that can meet those goals and requirements.

63 subarea. A portion of the SNA network subtask. In the context of z/OS multitasking, a consisting of a subarea node, attached task that is initiated and terminated by a higher peripheral nodes, and associated resources. order task (the main task). Subtasks run the Within a subarea node, all network accessible parallel functions, those portions of the units (NAUs), links, and adjacent link stations program that can run independently of the (in attached peripheral or subarea nodes) that main task program and each other. are addressable within the subarea share a common subarea address and have distinct superuser. (1) A system user who operates element addresses. without restrictions. A superuser has the special rights and privileges needed to subarea network. Interconnected subareas, perform administrative tasks. The z/OS their directly attached peripheral nodes, and equivalent is a user in privileged, or the transmission groups that connect them. supervisor, mode. (2) A system user who can pass all z/OS UNIX security checks. A subchannel set. Installation-specified superuser has the special rights and privileges structure that defines the placement of devices needed to manage processes and files. either relative to a channel subsystem or to an operating system. superuser authority. The unrestricted ability to access and modify any part of the operating subnet. Synonym for subnetwork. system, usually associated with the user who manages the system. subnetwork. (1) Any group of nodes that have a set of common characteristics, such as the supervisor. The part of z/OS that coordinates same network ID. (2) A distinct partitioned the use of resources and maintains the flow of piece of an internet network represented by processing unit operations. two or more sets of addresses that are subsets of the network's range of addresses. supervisor call (SVC). An instruction that (3) Synonymous with subnet. interrupts a program being executed and passes control to the supervisor so that it can subpool storage. All of the storage blocks perform a specific service indicated by the allocated under a subpool number for a instruction. particular task. support element (SE). (1) An internal control subsystem. A secondary or subordinate element of a processor that assists in many of system, or programming support, usually the processor operational functions. (2) A capable of operating independently of or hardware unit that provides communications, asynchronously with a controlling system. monitoring, and diagnostic functions to a Examples are CICS and IMS. central processor complex (CPC). subsystem interface (SSI). A component that provides communication between z/OS and its job entry subsystem.

64 Introduction to the New Mainframe: z/OS Basics suspended state. When only one of the SYN flood. A type of denial of service attack devices in a dual copy or remote copy volume in which a series of SYN packets are received pair is being updated because of either a in a short period of time. A SYN is the first permanent error condition or an authorized packet received when a remote host is user command. All writes to the remaining attempting a TCP connection. functional device are logged. This allows for automatic resynchronization of both volumes Synchronous Data Link Control (SDLC). A when the volume pair is reset to the active protocol for managing synchronous duplex state. information transfer over a data link connection. SVC. supervisor call. synchronous messages. WTO or WTOR SVC dump. A dump generated by a messages issued by a z/OS system during supervisor call (SVC). certain recovery situations.

SVC interruption. An interruption caused by syncpoint manager. A function that the execution of a supervisor call instruction, coordinates the two-phase commit process for causing control to be passed to the supervisor. protected resources, so that all changes to data are either committed or backed out. In SVC routine. A control program routine that z/OS, RRS can act as the system level performs or begins a control program service syncpoint manager. A syncpoint manager is specified by a supervisor call instruction. also known as a transaction manager, syncpoint coordinator, or a commit SWA. scheduler work area. coordinator. swap data set. A data set dedicated to the syntax. The rules governing the structure of a swapping operation. programming language and the construction of a statement in a programming language. swapping. A z/OS paging operation that writes the active pages of a job to auxiliary SYSIN. A system input stream; also, the name storage and reads pages of another job from used as the data definition name of a data set auxiliary storage into central storage. in the input stream. switch. A device that provides connectivity SYSLIB. (1) A subentry used to identify the capability and control for attaching any two target library in which an element is installed. ESCON or FICON links together. (2) A concatenation of macro libraries to be used by the assembler. (3) A set of routines switched multimegabit data service used by the link-edit utility to resolve (SMDS). A high-speed technology offered by unresolved external references. telephone companies in the United States. SYSLOG. system log. SYN. synchronize sequence numbers. SYSMOD. system modification.

65 SYSOUT. A system output stream; also, an system authorization facility (SAF). An indicator used in data definition statements to interface defined by z/OS that enables signify that a data set is to be written on a programs to use system authorization services system output unit. in order to protect access to resources such as data sets and z/OS commands. The IBM SYSOUT class. A category of output with Security Server is a product that uses the SAF specific characteristics and written on a interface. specific output device. Each system has its own set of SYSOUT classes, designated by a system board. In a personal computer (PC), character from A to Z, a number from 0 to 9, or the main circuit board that supports a variety a *. of basic system devices, such as a keyboard or a mouse, and provides other basic system sysplex. A set of z/OS systems functions. communicating and cooperating with each other through certain multisystem hardware system console. In z/OS, a console attached components and software services to process to the processor controller used to initialize a customer workloads. See Parallel Sysplex. z/OS system. sysplex couple data set. A couple data set system control element (SCE). Hardware that contains sysplex-wide data about that handles the transfer of data and control systems, groups, and members that use XCF information associated with storage requests services. All z/OS systems in a sysplex must between the elements of the processor. have connectivity to the sysplex couple data set. See couple data set. system data. The data sets required by z/OS or its subsystems for initialization. sysplex distributor. A software function in z/OS that increases availability through a System Display and Search Facility (SDSF). combination of dynamic VIPA and the z/OS A panel-based product that provides detailed Workload Manager. information about jobs and job output, devices (printers, punches, initiators, lines, spool Sysplex Timer. A hardware device that offloaders and spool volumes) and other synchronizes the time-of-day (TOD) clocks in resources in a z/OS system. multiple processors or processor sides. system library. A collection of data sets or SYSRES. system residence disk. files in which the parts of an operating system are stored. system. The combination of a configuration (hardware) and the operating system system management facilities (SMF). A (software). Often referred to simply as the z/OS component that provides the means for z/OS system. gathering and recording information for evaluating system usage. system abend. An abend caused by the operating system's inability to process a routine; may be caused by errors in the logic of the source routine.

66 Introduction to the New Mainframe: z/OS Basics system modification (SYSMOD). In SMP/E, system-managed storage. Storage managed the input data that defines the introduction, by the storage management subsystem (SMS) replacement, or updating of elements in the of z/OS. operating system and associated distribution libraries to be installed. A system modification Systems Network Architecture (SNA). The is defined by a set of modification control description of the logical structure, formats, statements (MCSs). protocols, and operational sequences for transmitting information units through, and System Modification Program Extended controlling the configuration and operation of, (SMP/E). An IBM program product, or an networks. The layered structure of SNA allows element of OS/390 or z/OS, used to install the ultimate origins and destinations of software and software changes on z/OS information, that is, the users, to be systems. SMP/E consolidates installation independent of and unaffected by the specific data, allows more flexibility in selecting SNA network services and facilities used for changes to be installed, provides a dialog information exchange. interface, and supports dynamic allocation of data sets. SMP/E is the primary means of controlling changes to the z/OS operating system. T system operator. A person responsible for T2.0. type 2.0 node. performing system-oriented procedures. T2.1. type 2.1 node. system programmer. A person who plans, T4. type 4 node. generates, maintains, extends, and controls the use of an operating system with the aim of T5. type 5 node. improving overall productivity of an installation. tailgate. The lower portion of the hardware system queue area (SQA). In z/OS, an area frame. The tailgate allows access to the I/O of virtual storage reserved for system-related and other types of wiring and cables from control blocks. internal mainframe parts. This internal wiring and cabling emerges from the tailgate and system services control point (SSCP). A usually is routed underneath the raised floor. focal point in an SNA network for managing configuration, coordinating network-operator tape. A thin, flexible magnetic strip on which and problem-determination requests, and data can be stored. providing directory support or other session services for network users. Multiple SSCPs, tape volume. Storage space on tape, cooperating as peers, can divide the network identified by a volume label, which contains into domains of control, with each SSCP data sets or objects and available free space. controlling the physical and logical units in its A tape volume is the recording space on a domain. single tape cartridge or reel. See volume. system-managed data set. A data set that has been assigned a storage class.

67 target library. In SMP/E, a collection of data telecommunication line. (1) The portion of a sets in which the various parts of an operating data circuit external to a data system are stored. These data sets are circuit-terminating equipment (DCE) that sometimes called system libraries. connects the DCE to a data-switching exchange (DSE), that connects a DCE to one target zone. In SMP/E, a collection of VSAM or more other DCEs, or that connects a DSE records describing the target system macros, to another DSE. (2) Any physical medium, modules, assemblies, load modules, source such as a wire or microwave beam, that is modules, and libraries copied from DLIBs used to transmit data. Synonymous with during system generation, and the SYSMODs transmission line. applied to the target system. Telnet. In the Internet suite of protocols, a task. In a multiprogramming or protocol that provides remote terminal multiprocessing environment, one or more connection service. It allows users of one host sequences of instructions treated by a control to log on to a remote host and interact as program as an element of work to be directly attached terminal users of that host. accomplished by a computer. temporary data set. A data set that is created task control block (TCB). A data structure and deleted in the same job. that contains information and pointers associated with the task in process. terabyte. For processor storage, real and virtual storage, and channel volume, 2 to the TB. terabyte. 40th power or 1 099 511 627 776 bytes. For disk storage capacity and communications TCB. task control block. volume, 1 000 000 000 000 bytes.

TCO. total cost of ownership. terminal. In data communication, a device, usually equipped with a keyboard and display TCP. Transmission Control Protocol. device, capable of sending and receiving TCP/IP. Transmission Control information. Protocol/Internet Protocol. terminal owning region (TOR). A CICS TDM. topology database manager. region devoted to managing the terminal network. TDU. topology data update. TG. transmission group.

TGTLIB. target library.

TGV. transmission group vector.

TH. transmission header.

68 Introduction to the New Mainframe: z/OS Basics third generation language (3GL). A token ring network. (1) According to IEEE high-level programming language that was 802.5, network technology that controls media designed to run on the third generation of access by passing a token (special packet or computer processors, built on integrated frame) between media-attached stations. (2) A circuit technology roughly from 1965 to 1970. FDDI or IEEE 802.5 network with a ring C, FORTRAN, Basic and Pascal are examples topology that passes tokens from one of third-generation languages still in use today. attaching ring station (node) to another. (3) See local area network. throughput. A measure of the amount of information transmitted over a network in a topology database update (TDU). A given period of time. Throughput is a measure message about a new or changed link or node of performance. It is generally measured in that is broadcast among APPN network nodes bits per second (bps), kilobits per second to maintain the network topology database, (Kbps), megabits per second (Mbps), or which is fully replicated in each network node. gigabits per second (Gbps). A TDU contains information that identifies the following: tightly coupled. Multiple CPs that share storage and are controlled by a single copy of topology database. See local topology z/OS. See loosely coupled, tightly coupled database, network topology database. multiprocessor. ToS. type of service. tightly coupled multiprocessing. Two computing systems operating simultaneously total cost of ownership (TCO). A under one control program while sharing methodology for calculating the actual cost of resources. owning a product over the period of ownership and use based on combining costs of tightly coupled multiprocessor. Any CPU acquisition or leasing, training, deployment, with multiple CPs. support, residual equipment values, return on investment, time to market, and so forth. /Extensions (TSO/E). The facility in z/OS that allows users to TP. transmission priority. interactively share computer time and resources. track. A circular path on the surface of a disk or diskette on which information is time-out. The time in seconds that the storage magnetically recorded and from which control remains in a “long busy” condition recorded information is read. before physical sessions are ended. transaction. A unit of work performed by one TLIB. target library. or more transaction programs, involving a specific set of input data and initiating a TLS. Transport Layer Security. specific process or job.

TN3270. Telnet/3270. transistor. A small solid-state device used in semiconductors to amplify an electrical signal, TN3270E. Telnet/3270 Enhanced. and switch electrical current on and off.

69 transit area. In the OSPF protocol, a routing transmission line. Synonymous with area that can have traffic passing through it. telecommunication line.

Transmission Control Protocol (TCP). A transmission priority. A rank assigned to a communications protocol used in the Internet message unit that determines its precedence and in any network that follows the U.S. for being selected by the path control Department of Defense standards for component in each node along a route for internetwork protocol. TCP provides a reliable forwarding to the next node in the route. host-to-host protocol between hosts in packet-switched communications networks transport layer. A network service that and in interconnected systems of such provides end-to-end communications between networks. It uses the Internet Protocol (IP) as two parties, while hiding the details of the the underlying protocol. communications network. The TCP and ISO TP4 transport protocols provide full-duplex Transmission Control Protocol/Internet virtual circuits on which delivery is reliable, Protocol (TCP/IP). A hardware independent error free, sequenced, and duplicate free. communication protocol used between UDP provides no guarantees (the physically separated computers. It was connectionless RPC protocol provides some designed to facilitate communication between guarantees on top of UDP). computers located on different physical networks. Transport Layer Security (TLS). A protocol standard that uses encryption to provide transmission group (TG). (1) A connection confidentiality and authentication between two between adjacent nodes that is identified by a TCP/IP applications. transmission group number. (2) In a subarea network, a single link or a group of links transport protocol. A specification of the between adjacent nodes. When a rules governing the exchange of information transmission group consists of a group of between components of a transport network. links, the links are viewed as a single logical link, and the transmission group is called a TRK. A subparameter of the SPACE multilink transmission group (MLTG). A parameter in a DD statement. It specifies that mixed-media multilink transmission group space is to be allocated by tracks. (MMMLTG) is one that contains links of TRL. transport resource list. different medium types (for example, token-ring, switched SDLC, nonswitched TRLE. transport resource list element. SDLC, and frame-relay links). trunk. In telephony, circuits that connect two transmission header (TH). Control switching systems, as opposed to connecting information, optionally followed by a basic a customer line to a switching system. information unit (BIU) or a BIU segment, that is created and used by path control to route trunk cable. Cables used to make permanent message units and to control their flow within connections between cabinets and which the network. See path information unit. remain in place even when not in use.

70 Introduction to the New Mainframe: z/OS Basics TSO. Time-sharing option. See Time Sharing unit of recovery (UR). A set of changes on Option/ Extensions (TSO/E). one node that is committed or backed out as part of an ACID transaction. A UR is implicitly TSO/E. Time Sharing Option/Extensions. started the first time a resource manager touches a protected resource on a node. A UR TSR. target service responsiveness. ends when the two-phase commit process for the ACID transaction changing it completes. twisted pair. A transmission medium that consists of two insulated electrical conductors UNIX file system. A section of the UNIX file twisted together to reduce noise. tree that is physically contained on a single device or disk partition and that can be separately mounted, dismounted, and U administered. See hierarchical file system, zSeries® File System. UCB. . UNIX operating system. An operating UCLIN. In SMP/E, the command used to system, developed by Bell Laboratories, that initiate changes to SMP/E data sets. Actual features multiprogramming in a multiuser changes are made by subsequent UCL environment. The UNIX operating system was statements. originally developed for use on minicomputers, but has been adapted for mainframes and UDP. User Datagram Protocol. microcomputers. The AIX operating system is IBM's implementation of the UNIX operating UID. user identifier. system. See z/OS UNIX System Services.

UIM. unit information module. unload. In SMP/E, to copy data out of SMP/E data set entries in the form of UCL statements, Unicode. (1) A universal character encoding by use of the UNLOAD command. standard that supports the interchange, processing, and display of text that is written in UNLOAD command. The SMP/E command any of the languages of the modern world. It used to copy data out of SMP/E data set also supports many classical and historical entries in the form of UCL statements. texts in a number of languages. The Unicode standard has a 16-bit international character unused cable. Physical cables that have been set defined by ISO 10646. (2) An international recently disconnected, but not yet placed in character encoding scheme that is a subset of inventory. the ISO 10646 standard. Each character supported is defined using a unique 2-byte upwardly compatible. The ability for code. See Extended Binary Coded Decimal applications to continue to run on later Interchange Code, American Standard Code releases of z/OS, without the need to for Information Interchange. recompile or relink. uniprocessor (UP). A processor complex that URG. urgent flag. has one central processor.

71 user abend. A request made by user code to V=V region. Synonymous with pageable the operating system to abnormally terminate region. a routine. Contrast with system abend. variable-length record. A record having a user catalog. An optional catalog used in the length independent of the length of other same way as the master catalog and pointed records with which it is logically or physically to by the master catalog. It also lessens the associated. Contrast with fixed-length record. contention for the master catalog and facilitates volume portability. VB. Variable blocked.

User Datagram Protocol (UDP). In the vendor. A person or company that provides a Internet suite of protocols, a protocol that service or product to another person or provides unreliable, connectionless datagram company. service. It enables an application program on one machine or process to send a datagram to version. A separate licensed program that is an application program on another machine or based on an existing licensed program and process. UDP uses the Internet Protocol (IP) that usually has significant new code or new to deliver datagrams. functions. Contrast with release and modification level. user exit. A routine that takes control at a specific point in an application. User exits are VIO. virtual input/output. often used to provide additional initialization VIPA. virtual IP address. and termination functions. virtual address space. In virtual storage user ID. user identification. systems, the virtual storage assigned to a job, user identification (user ID). A 1-8 character terminal user, or system task. See address symbol identifying a system user. space. user modification (USERMOD). In SMP/E, a virtual input/output (VIO). The allocation of change constructed by a user to modify an data sets that exist in paging storage only. existing function, add to an existing function, virtual IP address (VIPA). An IP address that or add a user-defined function. USERMODs is not associated with any physical interface. are identified by the ++USERMOD statement. virtual private network (VPN). A general USERMOD. user modification. term to describe a secure tunnel (data stream) UTP. unshielded twisted pair. between two endpoints. The term does not describe a protocol. The industry standard protocol for a VPN is an architecture called IP Security Architecture (IPSec). V

V=R region. Synonymous with nonpageable region.

72 Introduction to the New Mainframe: z/OS Basics virtual route (VR). (1) In SNA, either (a) a VLAN. virtual LAN. logical connection between two subarea nodes that is physically realized as a particular VM. Virtual Machine. explicit route or (b) a logical connection that is contained wholly within a subarea node for VOLSER. volume serial number. intranode sessions. A virtual route between volume. (1) The storage space on DASD, tape distinct subarea nodes imposes a or optical devices, which is identified by a transmission priority on the underlying explicit volume label. (2) That portion of a single unit route, provides flow control through virtual of storage which is accessible to a single route pacing, and provides data integrity read/write mechanism, for example, a drum, a through sequence numbering of path disk pack, or part of a disk storage module. (3) information units (PIUs). A recording medium that is mounted and virtual storage. (1) The storage space that demounted as a unit, for example, a reel of can be regarded as addressable main storage magnetic tape or a disk pack. by the user of a computer system in which volume backup. Backup of an entire volume virtual addresses are mapped into real to protect against the loss of the volume. addresses. The size of virtual storage is limited by the addressing scheme of the volume serial number. A number in a volume computer system and by the amount of label that is assigned when a volume is auxiliary storage available, not by the actual prepared for use in the system. number of main storage locations. (2) An addressing scheme that allows external disk volume table of contents (VTOC). A table on storage to appear as main storage. a direct access storage device (DASD) volume that describes the location, size, and other virtual storage access method (VSAM). An characteristics of each data set on the volume. access method for direct or sequential processing of fixed-length and varying-length VPN. virtual private network. records on direct access devices. The records in a VSAM data set or file can be organized in VR. virtual route. logical sequence by a key field (key sequence), in the physical sequence in which VRN. virtual routing node. they are written on the data set or file (entry-sequence), or by relative-record VSAM. virtual storage access method. number. VTAM. Virtual Telecommunications Access virtual telecommunications access method Method. (VTAM). A set of programs that maintain VTOC. volume table of contents. control of the communication between terminals and application programs running under z/OS. Now known as Communications Server - SNA Services. W

VIT. VTAM internal trace. wait state. Synonymous with waiting time.

73 waiting time. (1) The condition of a task that work request. A piece of work, such as a depends on one or more events in order to request for service, a batch job, an APPC, enter the ready condition. (2) The condition of CICS, or IMS transaction, a TSO LOGON, or a a processing unit when all operations are TSO command. suspended. workload. A group of work to be tracked, WAN. wide area network. managed and reported as a unit.

WAP. wireless access point. workload management (WLM). A z/OS component that prioritizes workloads and WCC. write control character. matches them with available resources.

WebSphere®. An IBM brand name that wrap mode. The console display mode that encompasses tools for developing e-business allows a separator line between old and new applications and middleware for running Web messages to move down a full screen as new applications. messages are added. When the screen is filled and a new message is added, the WebSphere Application Server. Web separator line overlays the oldest message application server software that runs on a Web and the newest message appears immediately server and that can be used to deploy, before the line. integrate, execute, and manage e-business applications. write-to-operator (WTO) message. A message sent to an operator console WebSphere MQ. A family of IBM licensed informing the operator of errors and system programs that provides message queuing conditions that may need correcting. services. write-to-operator-with-reply (WTOR) well-known port. In Internet communications, message. A message sent to an operator one of a set of preassigned protocol port console informing the operator of errors and numbers that address specific functions used system conditions that may need correcting. by transport level protocols (for example, TCP The operator must enter a response. and UDP). WSF. write structured field. wide area network (WAN). A network that provides communication services between WTO. write-to-operator. devices in a geographic area larger than that served by a local area network (LAN) or a WTOR. write-to-operator-with-reply. metropolitan area network (MAN).

Wi-Fi. wireless fidelity. X wild carding. The use of an asterisk (*) as a multiple character replacement in XA. Extended Architecture. classification rules. XCA. external communication adapter. WLM. workload management.

74 Introduction to the New Mainframe: z/OS Basics XCF. cross-system coupling facility. zSeries Application Assist Processor (zAAP). A specialized processing assist unit XID. exchange ID. configured for running Java programming on selected zSeries machines.

zSeries File System (zFS). A z/OS UNIX file Z system that stores files in VSAM linear data sets. z/Architecture. An IBM architecture for mainframe computers and peripherals. The zSeries family of servers uses the z/Architecture. Numerics z/OS. A widely used operating system for IBM 16MB boundary. A notional boundary in mainframe computers that uses 64-bit central virtual storage. Addresses below the 16MB storage. boundary can be accessed by 24-bit or 31-bit addressing. Addresses on or above the 16MB z/OS Language Environment. An IBM boundary can be accessed only by 31-bit software product that provides a common addressing. The numerical value of 16MB is 2 runtime environment and common runtime to the power of 24, or 16,777,216. services for conforming high-level language compilers. 16 megabyte line. Synonym for 16MB boundary. z/OS UNIX System Services (z/OS UNIX). z/OS services that support a UNIX-like 3270 application. An application on a host environment. Users can switch between the system accessed by a 3270 terminal device. traditional TSO/E interface and the shell Typically, 3270 applications run under CICS or interface. UNIX-skilled users can interact with IMS. the system, using a familiar set of standard commands and utilities. z/OS-skilled users can 3270 data stream. The commands, control interact with the system, using familiar TSO/E codes, orders, attributes, and data or commands and interactive menus to create structured fields for 3270 devices that are and manage hierarchical file system files and transmitted between an application program to copy data back and forth between z/OS and a terminal. Data being transferred from or data sets and files. Application programmers to an allocated primary or tertiary device, or to and users have both sets of interfaces to the host system, as a continuous stream of choose from and, by making appropriate data and 3270 Information Display System trade-offs, can choose to mix these interfaces. control elements in character form. zAAP. zSeries Application Assist Processor. 3270 pass-through mode. A mode that lets a program running from the z/OS shell send and zFS. zSeries file system. receive a 3270 data stream or issue TSO/E commands. zSeries. IBM enterprise servers based on z/Architecture. 3GL. third generation language.

75 76 Introduction to the New Mainframe: z/OS Basics Notices

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© Copyright IBM Corp. 2006. All rights reserved. 77 Trademarks

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78 Introduction to the New Mainframe: z/OS Basics