z/OS MVS Programming: JES Common Coupling Services
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Attach processing

z/OS MVS Programming: JES Common Coupling Services
SA23-1387-00

JES2 and JES3 attach processing are basically equivalent as shown in section A of Figure 1. During JES initialization processing:

  1. JES issues macro IXZXIXAT which causes exit IXZXIT03 to get control
  2. IXZXIT03 first obtains storage from subpool 241 if storage is needed for the subsequent calls to IXZXIT01 and IXZXIT02.
  3. Exit IXZXIT03 then optionally issues macro IXZXIXAT to establish a second attachment to the JES-defined group or to establish an installation-defined JES XCF group.
  4. JES then continues initialization processing.

Attention:

Whenever you issue the IXZXIXAT macro, each invocation causes exit IXZXIT03 to get control. If you do not code IXZXIT03 to prevent subsequent recursive calls, JES XCF attempts to again attach the installation-defined member, and JES XCF produces a dump. Figure 1 provides a graphic view of the IXZXIXAT call from JES initialization to attach JES XCF group N1 and then an installation-supplied call to attach installation group MINE. The figure also illustrates one coding technique that uses the set of CLC and BNE instructions to prevent an attempted reattach of installation group MINE. Be certain to add similar code if you attach an installation-defined group.
Figure 1. Example attach (IXZXIT03) code
Example attach (IXZXIT03) code
Parent topic: Exit Routine Processing

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