Assembler for Exits

With IBM's latest mainframe announcements, perhaps it is time to consider that z/OS does have a future, and that some of the skills that have been lost will need to be replicated. One classic example of this is Assembler. It used to be that every new z/OS Systems Programmer was taught to write Assembler as a matter of course. This has not been the case for quite some time. This means that upgrades to the z/OS operating system are heavily reliant on finding one of the "Old Guys or Gals" to review your exit code and establish if any changes are required for the new z/OS release.

This course is designed for competent z/OS Systems Programmers with no prior knowledge of the Assembler Language.

Delegates should be existing z/OS Systems Programmers.

A working knowledge of TSO/ISPF is assumed.

The ability to write Assembler code is not required.

This course takes a unique approach in that the ability to write Assembler is not a prerequisite. Using a combination of NLP/Brain Friendly techniques we take any competent Systems Programmer and teach them to read their own environment's system exits in three days.

• Module 1: Assembler for non-Assembler Programmers.
  • Assembler documentation sources.
  • Statement layout
  • Compilation differences
  • Starting and ending a module
  • General Purpose Registers and conventional use
  • Working Storage and some field definitions
  • The lack of data structures
  • How to redefine memory and fields
  • Decision making
  • Input / Output processing
  • Moving data around
  • Mathematics and Editing data
  • Invoking sub-routines and passing parameters
  • Exploiting z/OS Services
• Module 2: Instruction Types
  • Traditional instructions
    • RR – Format
    • RS – Format
    • RX – Format
    • SI – Format
    • SS - Format
  • More modern interpretations
    • 2-byte Format
    • 4-byte Format
    • 6-byte Format
  • General instructions versus Privileged Instructions
• Module 3: Reference Material
  • General reference material
  • Types of exits, and their reference material
    • BCP Exits
    • CICS Exits, GLUES and TRUES
    • IMS Exits
    • IPCS Exits
    • JES2 Exits
    • JES3 Exits
    • RACF Exits
    • RMF Exits
    • SMF Exits
    • SMS Exits
    • TSO Exits
    • VTAM Exits
    • z/OS Exits include MPFLST
  • User Supervisor Call (SVC)
• Module 4: Coding Requirements
  • What is re-entrant code?
  • Why have Re-Entrant Code?
  • What are the benefits of Re-Entrant code?
  • Re-Entrant code requirements
  • Avoiding in-line parameter lists
  • Acquiring memory – STORAGE Macro
  • Releasing memory – STORAGE Macro
  • AMODE / RMODE switching
  • RSECT versus CSECT
  • Exercise in converting non-reentrant to re-entrant code
  • Where to store exits
  • Testing
• Module 5: New Release Changes
  • Is the exit still required?
  • A scenario
  • MPFLIST versus AUTORxx PARMLIB member
  • The introduction and Release Guide
  • Manuals and sample Exit Source Code
• Module 6: Reading what is there
  • Is the source code available?
  • Here are two samples that can be reviewed
    • A least one message handling exit triggered via the MPFLST
    • IKJEFF10 the TSO Submit Exit
  • What if the source code is not available.
    • AMBLIST Service Aid to produce list of CSECT in a multi-CSECT module
    • AMASPZAP Service Aid to produce a CSECT listing
    • Link-Editor to isolate a CSECT
    • ASMDASM – Disassembler object code to source
• Module 7: Review of customer exits
  • The content for this module will depend upon what the client is prepared to disclose.
  • If there is no client content module 6 will have achieved this goal albeit in an abstract fashion.