Designing an XZIQUE global user exit program

The functions of your XZIQUE exit should be designed to perform the following operations:
  1. To control of the number of tasks (and the amount of associated resource) that are waiting in a queue for a free intersystem session. Waiting tasks can degrade the performance of the local system.
  2. To detect poor response from the receiving (remote) system and to notify the operator (or automatic operations program).
  3. To cause CICS® to issue a message when the link resumes normal operation.

The XZIQUE global user exit parameter list is designed to support these objectives.

Sample XZIQUE exit program

A sample XZIQUE exit program, DFH$XZIQ, is provided. You can use the sample program as a base to design your own global user exit program. The sample is supplied in the CICSTSnn.CICS.SDFHSAMP library. The DSECT object DFHXZIDS, which is used by the sample program to map the area addressed by UEPZDATA, is supplied in the CICSTSnn.CICS.SDFHMAC library. CICSTSnn is your CICS release.

For example, you can find them in CICSTS64.CICS.SDFHSAMP and CICSTS64.CICS.SDFHMAC if your CICS system is at CICS TS beta.

For more information about DFH$XZIQ, see MRO and APPC session queue management sample exit program: DFH$XZIQ.

Design considerations

The information passed at XZIQUE is designed to enable your XZIQUE global user exit program to:
  • Avoid false diagnosis of problems on the connection by distinguishing poor response times from a complete bottleneck.
  • Ensure that a link resumes normal operation quickly and without operator intervention once any problem in a remote system is resolved.

Some guidance on the use of IRC/ISC statistics

CICS adds an entry for unsatisfied allocate requests to the non-specific (generic) allocate queue, and the specific modegroup allocate queue.

Non-specific (generic) allocate queue
All non-specific allocate requests are queued in this single queue. CICS makes the total number of entries in this queue available in the system entry statistics field A14ESTAQ, to which your global user exit program has access by means of the address of the system entry statistics, which is passed in UEPCONST.
Specific modegroup allocate queues
Specific allocate requests are queued in the appropriate modegroup queue, one queue for each specific modegroup name. CICS makes the total number of entries in all these queues available, as a single total, in the mode entry statistics field A20ESTAQ, to which your global user exit program has access by means of the address of the mode entry statistics, which is passed in UEPMODST.

For detailed information about statistics fields, see ISC/IRC system entry: Resource statistics.