Datenverwaltung, Ein-/Ausgabe it-Akademie Bayern z/OS und OS/390 Lehrgang 2008 Prof. Dr.-Ing. Wilhelm G. Spruth Teil 8 Adressierung des Ein-/Ausgabe Subsystems EA 0701 ww6 © copyright W. G. Spruth, 08-2004 wgs 10-02 Adressierung im Ein-/Ausgabe Subsystems IBM zSeries Connectivity Handbook International Technical Support Organization, May 2003 SG24-5444-03 f:\grx\redbooks\connect1.pdf Devices System z verwendet den Begriff “Device”, eine Abkürzung für I/O Device. Typische Devices sind • Plattenspeicher (DASD, Disk Drive), • Magnetbänder, • Drucker, • .......... Heute werden fast ausschließlich logische DASDs vom Typ 3390 eingesetzt. Diese werden von einem Enterprise Storage Subsystem (ESS) auf regulären 3 ¼ Zoll Platten emuliert. Devices werden von einem System mit Hilfe eines Device Identifiers adressiert Early system design The DASD (disk drive) marked with an X has address 132, derived as shown below 8 Bit 8 Bit Device Address The disk drive marked with an Y can be addressed as 171, 571, or 671 because it is connected through three channels. By convention the device is known by its lowest address (171), but all three addresses could be used by the operating system to access the disk drive. Multiple paths to a device are useful for performance and for availability. When an application wants to access disk 171, the operating system will first try channel 1. If it is busy (or not available), it will try channel 5, and so forth. Shown is another S/360 system with two channels connected to control units used by the first system. This sharing of I/O devices is common in all mainframe installations. Tape drive Z is address A31 for the first system, but is address 331 for the second system. Current mainframes use a different approach. In the good old S/360 days, a device address such as 583 meant channel 5, control unit 8, device 3 and this was the address of the device. No S/390 machines work this way today, but the old terminology is often used. This terminology is technically incorrect, but is so widely used that you must understand it. If someone tells you to “IPL from address 583” they really mean to IPL from device number 583. For all S/390 machines, the hardware address of a device will be something like chipd 05, CU 3, UA 7. This is similar to the old S/390 addresses; a chpid is a channel, the CU number is a control unit address, and the UA is a unit address (that can normally range up to x’FF’). However, the software never sees this hardware address. The S/390 I/O subsystem, using the IOCDS data, converts the chpid/CU/UA “hardware address” into a device number. The operating system uses the device number to connect to I/O devices. The operating system and applications never see the actual hardware addresses (the chpid, CU, and UA numbers). Historische Entwicklung Parallel-I/O-interface For a channel path of the parallel-I/O-interface type, the device identifier is called a device address (unit address) and consists of an eight-bit value. ESCON-I/O interface For the ESCON-I/O interface, the device identifier consists of a four-bit control-unit address and an eight-bit unit address . FICON-I/O interface For the FICON-I/O interface, the device identifier consists of an eight-bit control-unit-image ID (address) and an eight-bit unit address. The unit address (device address) identifies the particular I/O device (and, on the parallel-I/O- interface, the control unit) associated with a subchannel. E/A Konfigurations-Netzwerk Channel Subsystem Hauptspeicher FF ... FF CPU CPU CPU Benutzer Prozesse Ke r n e l SAP SAP 00 ... 00 HSA CH. CH. CH. CH. Kanäle Channel Subsystem CU CU CU CU CU CU CU = Control Unit Plattenspeicher Das Channel Subsystem wird durch mehrere Prozessoren (als System Assist Prozessoren, SAP, bezeichnet) und entsprechenden Code verwirklicht. Die SAPs greifen parallel zu den CPUs auf den Hauptspeicher zu und entlasten diese von Ein-/Ausgabe Aufgaben. Die HSA (Hardware System Area) ist ein Teil des Hauptspeichers. Sie liegt außerhalb des Adressenraums, auf den die CPUs zugreifen können. Das Channel Subsystem besteht aus SAP Prozessoren und Code in der HSA. Es bildet das virtuelle E/A Subsystem, mit dem der Betriebssystem Kernel glaubt zu arbeiten, auf die reale E/A Struktur ab. Es 0370 ww6 wgs 10-04 Haupt- CPU speicher 256 Kanäle Kanal Kanal Kanal Kanal Kanal CU CU CU CU CU 256 Devices pro CU CU CU CU CU Kanal max. S/390 Device Identifikation 0 7 8 15 16 Bit I/O Address Channel Device Address Address max. 256 Channels und max. 256 Devices pro Channel Heutige Konfiguration Die früheren parallelen Kanäle wurden durch serielle ESCON und FICON Kanäle ergänzt. Letztere werden gemeinsam als „Channel Path“ bezeichnet und durch eine 8 Bit Channel Path ID (CHPID) or physical channel identifiers (PCHIDs) gekennzeichnet. Ein Channel Subsystem kann maximal 256 Channel Path unterstützen. Auf eine Control Unit kann über unterschiedliche Channel Path zugegriffen werden, Heutige Konfiguration (3) Eine Ein/Ausgabe Einheit (Device), z.B. ein Plattenspeicher, wird eines 16 Bit Device Identifiers angesprochen. Für FICON besteht dieser aus einer 8 Bit Control Unit Nr. und einer 8 Bit Device Address. Letztere wird auch als Unit Address bezeichnet. 0 7 8 15 16 Bit Device Identifier Control Device Unit Nr. Address Auszug aus z/Architecture Principles of Operation (1) One subchannel is provided for and dedicated to each I/O device accessible to the channel sub- system. Up to 256 I/O devices can be addressed on a single parallel-I/O interface. Up to 256 devices can be attached to each control unit that uses the serial-I/O interface The channel subsystem provides information about associated I/O devices to CPUs, which obtain this information by executing I/O instructions. The actual number of subchannels provided depends on the model and the configuration; the maximum addressability is 65,536. The maximum addressability of channel paths provided by a channel subsystem is 256. Auszug aus z/Architecture Principles of Operation (2) A device identifier is an address, not apparent to the program, that is used by the channel subsystem to communicate with I/O devices. The type of device identifier used depends on the specific channel-path type and the protocols provided. Each subchannel contains one or more device identifiers. For the FICON-I/O inter-face, the device identifier consists of an eight-bit control-unit-image ID and an eight-bit device address. Identifikation von Fritz Müller Normalerweise: Fritz Müller geb. 21. Juni 1985 Geburtsort Augsburg Vater Staat benutzt statt dessen für die deutsche Rentenversicherung eine Nummer, z.B.: 970 63210685S048 11 die Fritz Müller eindeutig identifiziert. Identifikation von Fritz Müller System z Devices Normalerweise: Fritz Müller geb. 21. Juni 1985 Device Nr. Geburtsort Augsburg Vater Staat benutzt statt dessen für die deutsche Rentenversicherung eine Nummer, z.B.: 970 63210685S048 11 Device Identifier die Fritz Müller eindeutig identifiziert. Heutige Konfiguration (1) 4 Begriffe: Channel Path ID (CHPID) 8 Bit Subchannel Number 16 Bit Device Nr. (1 pro Subchannel) 16 Bit Device Identifier 16 Bit Der Device Identifier besteht aus einer 8 Bit Control Unit Address und einer 8 Bit Device Address. Die 8 Bit Device Address wird häufig auch als Unit Address bezeichnet und ist nicht zu verwechseln mit der 16 Bit Device Nr. Subchannel A subchannel provides the logical appearance of a device to the program and contains the information required for sustaining a single I/O operation. The subchannel consists of internal storage (UCW) that contains information in the form of a • CCW address, • channel-path identifier, • device number, as well as additional Information like count, status indications, and I/O-interruption sub-class code, path availability and functions pending or being performed. I/O operations are initiated with a device by exe- cuting I/O instructions that designate the subchannel associated with the device. Subchannel Number A subchannel number is a system-unique 16-bit value used to address a subchannel. The subchannel is addressed by eight I/O instructions: • CANCEL SUBCHANNEL, • CLEAR SUBCHANNEL, • HALT SUBCHANNEL, • MODIFY SUBCHANNEL, • RESUME SUBCHANNEL, • START SUBCHANNEL, • STORE SUBCHANNEL, and • TEST SUBCHANNEL. Each I/O device accessible to the channel subsystem is assigned a dedicated subchannel at installation time. All I/O functions relative to a specific I/O device are specified by the program by designating the subchannel assigned to the I/O device. Normally, subchannel numbers are only used in communication between the CPU program and the channel subsystem. START SUBCHANNEL Machine Instruction When START SUBCHANNEL is executed, parameters are passed to the target subchannel requesting that the channel subsystem perform a start function with the I/O device associated with the subchannel. The channel subsystem performs the start function by using information at the sub- channel, including the information passed during the execution of the START SUBCHANNEL instruction, to find an accessible channel path to the device. Once the device has been selected, execution of an I/O operation is accomplished by the decoding and executing of a CCW by the channel subsystem and the I/O device. Am operation-request block (ORB) is designated by a START SUBCHANNEL instruction. Subchannel Number • Device identification used for communication between z/OS and channel subsystem • 16 Bit, 65 536 possible devices • Index for the UCW table (Unit Control Word table) within the HSA. • Used by microcode during execution of the SSCH (Start Subchannel) machine instruction • Stored in the UCB at IPL time • Independent of device number • Used for communication between I/O Supervisor and Channel Subsystem (CSS) UCW Table UCW Subchannel Number Each device is identified to • humans by a 16- bit device number • the Channel Subsystem by a 16- bit subchannel number Subchannel Number A subchannel number is a system-unique 16-bit value used to address a subchannel.