Data conversion on z/OS

 

On z/OS, be aware of the following:

• Exit programs can be written in assembler language only.

• Exit programs must be reentrant, and capable of running anywhere in storage.

• Exit programs must restore the environment on exit to that at entry, and must free any storage obtained.

• Exit programs must not WAIT, or issue ESTAEs or SPIEs.

• Exit programs are usually invoked as if by z/OS LINK in:

  • Non-authorized problem program state

  • Primary address space control mode

  • Non cross-memory mode

  • Non access-register mode

  • 31 bit addressing mode

  • TCB-PRB mode

• When used by a CICS application, the exit is invoked by EXEC CICS LINK, and must conform to the CICS programming conventions. The parameters are passed by pointers (addresses) in the CICS communication area (COMMAREA).

  Although not recommended, user exit programs can also use CICS API calls, with the following caution:

  • Do not issue syncpoints, as the results could influence units of work declared by the MCA.

  • Do not update any resources controlled by a resource manager other than WebSphere MQ for z/OS, including those controlled by CICS Transaction Server for OS/390.

• For distributed queuing without CICS, the exit is loaded from the data set referenced by the CSQXLIB DD statement.

• For distributed queuing using CICS, data-conversion exits are not supported.

 

Parent topic:

Invoking the data-conversion exit

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