z/OS 2.4 MVS Programming: Authorized Assembler Services Guide IBM SA23-1371-40 Note Before using this information and the product it supports, read the information in “Notices” on page 815. This edition applies to Version 2 Release 4 of z/OS (5650-ZOS) and to all subsequent releases and modifications until otherwise indicated in new editions. Last updated: 2021-06-21 © Copyright International Business Machines Corporation 1988, 2021. US Government Users Restricted Rights – Use, duplication or disclosure restricted by GSA ADP Schedule Contract with IBM Corp. Contents Figures................................................................................................................ xv Tables.................................................................................................................xxi About this information......................................................................................xxvii Who should use this information............................................................................................................xxvii How to use this information................................................................................................................... xxvii z/OS information.................................................................................................................................... xxviii How to send your comments to IBM................................................................... xxix If you have a technical problem.............................................................................................................. xxix Summary of changes......................................................................................... xxxi Summary of changes for z/OS Version 2 Release 4................................................................................xxxi Summary of changes for z/OS Version 2 Release 3...............................................................................xxxii Summary of changes for z/OS Version 2 Release 2 (V2R2), as updated March, 2016........................xxxiii Summary of changes for z/OS Version 2 Release 2 (V2R2), as updated December, 2015.................xxxiii Summary of changes for z/OS Version 2 Release 2..............................................................................xxxiii Chapter 1. Introduction......................................................................................... 1 Chapter 2. Subtask creation and control.................................................................5 Creating a new task (ATTACH or ATTACHX macro)..................................................................................... 5 Ensuring that a process completes (STATUS macro)..................................................................................5 Communicating with a program (EXTRACT, QEDIT)................................................................................... 6 Providing an EXTRACT answer area.......................................................................................................8 Chapter 3. Program management.........................................................................11 Residency and addressing mode of programs..........................................................................................11 Placement of modules in storage........................................................................................................ 12 Addressing mode..................................................................................................................................12 Specifying where the module is to be loaded (LOAD macro)................................................................... 12 Synchronous exits (SYNCH or SYNCHX macro)........................................................................................ 13 Using checkpoint/restart........................................................................................................................... 13 Using re-entrant modules..........................................................................................................................14 Using LLACOPY to refresh LLA directories................................................................................................ 14 Changing the LNKLST concatenation........................................................................................................ 15 Changing the current LNKLST set........................................................................................................ 15 Monitoring dynamic LPA processing......................................................................................................... 15 Listing contents of dynamic LPA with CSVDLPAU............................................................................... 19 Monitoring dynamic exits processing........................................................................................................21 Monitoring fetch and unfetch processing..................................................................................................24 Chapter 4. Serialization....................................................................................... 29 Choosing a serialization service................................................................................................................ 29 Providing ENQ resource information on DISPLAY GRS command........................................................... 34 Locking....................................................................................................................................................... 34 Categories of locks............................................................................................................................... 35 iii Types of locks....................................................................................................................................... 35 Locking hierarchy................................................................................................................................. 36 CML lock considerations...................................................................................................................... 36 Obtaining, releasing, and testing locks (SETLOCK)............................................................................. 37 Suspend lock instrumentation data ....................................................................................................37 Using the must-complete function (ENQ/DEQ)........................................................................................ 38 Characteristics of the must-complete function...................................................................................38 Programming notes.............................................................................................................................. 39 Shared direct access storage devices (shared DASD).............................................................................. 39 Volume/device status...........................................................................................................................40 Volume handling...................................................................................................................................40 Macros used with shared DASD (RESERVE, EXTRACT, GETDSAB)..................................................... 40 Serializing parallel tasks (WAIT and POST).............................................................................................. 46 Asynchronous cross memory POST.....................................................................................................47 Synchronous cross memory post.........................................................................................................48 Bypassing the POST routine.................................................................................................................48 Waiting for event completion (EVENTS).............................................................................................. 48 Writing POST exit routines.........................................................................................................................49 Identifying and deleting exit routines..................................................................................................49 Initializing extended ECBs and ECB extensions..................................................................................49 POST interface with exit routines........................................................................................................ 50 Re-entry to POST from a POST exit..................................................................................................... 51 Branch entry to the POST service routine.................................................................................................51 Branch entry to the WAIT service routine.................................................................................................53 Serializing RB processing...........................................................................................................................54 Suspending an RB until an event completes (SUSPEND)....................................................................54 Using the CALLDISP macro.................................................................................................................