z/OS 2.4 JES2 Installation Exits IBM SA32-0995-40 Note Before using this information and the product it supports, read the information in “Notices” on page 439. 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: 2021-05-23 © Copyright International Business Machines Corporation 1988, 2020. US Government Users Restricted Rights – Use, duplication or disclosure restricted by GSA ADP Schedule Contract with IBM Corp. Contents Figures............................................................................................................. xxiii Tables................................................................................................................xxv About this document........................................................................................ xxvii Who should use this document.............................................................................................................. xxvii How this document is organized............................................................................................................ xxvii Where to find more information............................................................................................................. xxvii Additional information............................................................................................................................ xxvii 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 (V2R4)................................................................... xxxi Summary of changes for z/OS Version 2 Release 3 (V2R3)................................................................... xxxi Summary of changes for z/OS Version 2 Release 2 (V2R2)................................................................... xxxi Chapter 1. Introduction......................................................................................... 1 What is a JES2 exit?..................................................................................................................................... 3 Environment............................................................................................................................................5 Chapter 2. Writing an exit routine...........................................................................7 Language...................................................................................................................................................... 7 Operating environment................................................................................................................................ 7 JES2 environments...................................................................................................................................... 7 Initialization data set checker................................................................................................................... 10 Synchronization......................................................................................................................................... 11 Reentrant code considerations................................................................................................................. 11 Linkage conventions.................................................................................................................................. 12 Addressing mode of JES2 exits................................................................................................................. 13 Addressing mode requirements.......................................................................................................... 13 Residency mode requirements............................................................................................................ 13 Received parameters.................................................................................................................................13 Return codes.............................................................................................................................................. 14 Control blocks............................................................................................................................................ 14 Determining the JES2 release level.......................................................................................................... 15 Service routine usage................................................................................................................................ 18 Exit logic..................................................................................................................................................... 18 Exit-to-exit communication.......................................................................................................................18 Exit point-to-exit routine communication.................................................................................................18 Exit routine-to exit point communication................................................................................................. 19 Exit-to-operator communication...............................................................................................................19 Required mapping macros.........................................................................................................................19 JES2 main task environment exits.......................................................................................................19 JES2 subtask environment exits..........................................................................................................20 Functional subsystem address space environment exits................................................................... 21 User environment exits........................................................................................................................ 21 User environment exit considerations...................................................................................................... 23 iii Reentrancy............................................................................................................................................23 Accessing CKPTed Data Area...............................................................................................................23 Accessing $CATs...................................................................................................................................23 Storage considerations........................................................................................................................ 24 One time exit initialization code................................................................................................................ 24 Tracing........................................................................................................................................................24 Recovery.....................................................................................................................................................25 Loading non-JES2 modules.......................................................................................................................25 Chapter 3. Controlling the loading of installation-defined load modules................ 27 Loading and placement of installation load modules............................................................................... 27 Dynamic Load Modules..............................................................................................................................29 Dynamic Load Module Considerations................................................................................................ 29 $$$$LOAD and $$$$DEL routines.......................................................................................................31 $$$$DEL Routine................................................................................................................................. 33 Special Considerations for LPA Modules............................................................................................. 35 Chapter 4. Enabling an exit.................................................................................. 37 Chapter 5. Getting listings of JES2 data areas.......................................................39 Chapter 6. Sample exit routines........................................................................... 41 Chapter 7. Multiple exit routines in a single module.............................................. 43 Chapter 8. Testing your exit routine......................................................................47 Packaging the exit......................................................................................................................................47 Initializing the exit in the system...............................................................................................................48 Passing control to exit