DB2 & IMS

The first step in resolving any problem is to determine where the problem actually lies. For example, if an IMS transaction managed by RRS hangs, the IMS Connect client application might time out the transaction request, but the UR might remain hung in IMS, RRS, or both. To resolve this situation, you’ll want to determine where the UR is hung. IMS Connect, IMS, and RRS together provide a variety of methods for determining where the problem lies.

With IMS Connect, you can issue the IMS Connect MVS command VIEWUOR to display the status of a specific UR or of all URs IMS Connect currently manages. In IMS itself, you can issue the command /DISPLAY UOR ALL to display the status of all URs in IMS. IMS may have any number of different types of URs other than those associated with IMS.

From the RRS ISPF panels you can view even more comprehensive RRS information for resource managers, work managers, URs, and log streams.

If necessary, take an SVC dump of the IMS control regions and dependent regions, the IMS Connect address space, the RRS address space, and the z/OS system logger address space.

You also can generate valuable diagnostic information by using the trace functions of IMS Connect recorder, the RRS component, and other associated components such as the IMS RRST table trace and IMS OTMT table trace.

Running RRS and IMS with the RRS CTRACE and the IMS OTMT and RRST traces is recommended. Also of particular use in diagnosing problems are the IMS Connect internal traces, HWSTRACE and BPETRACE, which you can view in a dump of IMS Connect in IMS Version 9. In IMS Version 10, you don’t need a dump to view the HWSTRACE and BPETRACE traces.

For IMS Connect traces, the default size of the IMS Connect trace tables can be small for diagnosing some problems, including those related to RRS. To ensure your trace tables capture as much useful information as possible, increase their sizes in the IMS BPECFG PROCLIB member. For example, the following size specifications, which define 200 4K pages, should be sufficient:

TRCLEV=(*,HIGH,BPE,PAGES=200)

TRCLEV=(*,HIGH,HWS,PAGES=200)

An additional source of diagnostic information is the IMS Online Log Data Set (OLDS), which also can provide detailed RRS diagnostic information.

If an IMS-dependent region hangs for a long time with a WAIT-RRS status, you can try issuing the IMS command “/ STOP REGION reg# ABDUMP transaction- name” to roll back the transaction and free the dependent region or you can use the RRS ISPF panels to abort the UR and get out of the wait state.

Keep Your IMS RRS-Related Maintenance Current

IMS Version 10 provides many enhancements that exploit z/OS features and provides effective RSS twophase commit processing. For example, the IMS Version 10 APAR PK37614 offers the complete outbound protected conversation support for transactions running in the IMS shared queues environment. If you use global transactions with IMS Connect transaction, or if you run IMS Connect with the IMS shared message queue support OTMA commit-then-send messages, ensure that your IMS maintenance is up-to-date with all the RRSrelated enhancements.

Conclusion

This article has suggested some methods for improving performance when IMS Connect, IMS, and RRS work together and has highlighted some of the diagnostic methods and resources available with these products. The IMS development team is committed to high-availability, performance, and data integrity, and continues to enhance IMS Connect support for two-phase commit processing with RRS. Z

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