System dumps

CICS produces a system dump using the MVS™ SDUMP macro.

MVS SDUMP macro

The MVS SDUMP dump results from CICS® issuing an MVS SDUMP macro. It includes almost the entire CICS address space, that is, the MVS nucleus and other common areas, as well as the CICS private storage areas. The SDUMP dump is written to an MVS dump data set, which you can process using the interactive problem control system (IPCS). For information about the SDUMP macro, and the associated MVS dump data sets, see the OS/390 MVS Diagnosis: Procedures manual.

The SDUMP macros issued by CICS normally contain the QUIESCE=NO parameter. They may not if the SDUMP is taken because of an abend in CICS SVC code or when altering MRO control blocks. This parameter allows the MVS system to remain dispatchable while the SDUMP is being taken, thus reducing the impact on the system. However if QUIESCE=YES is specified as an MVS system default it will override that specified by CICS. These defaults can be altered by using the MVS CHNGDUMP command. For more information on this command see the OS/390 MVS System Commands manual.

You should use the MERGE function when changing the SDUMP options by the CHNGDUMP command to ensure that the areas selected by CICS to dump are included in the MVS dump data set output. If you use the ADD option, it replaces any options specified by CICS when issuing the SDUMP in many cases. This can result in partial dumps being taken to the MVS dump data set. MVS always includes LSQA and TRT in the dump but may exclude the private area if you use the wrong options in the update by the CHNGDUMP command. You must thoroughly review your use of the CHNGDUMP command when setting up your CICS region. For information about the CHNGDUMP command and the effect that altering its options has on the dump output from CICS, see the OS/390 MVS Initialization and Tuning Guide.

If you are running CICS with XRF, the surveillance signal of the active CICS region stops during an MVS SDUMP of the active CICS region’s address space, which could lead to unnecessary takeovers being initiated, if the ADI (alternate delay interval) for the alternate is set too low. However, you can prevent SDUMPs of other address spaces from causing unnecessary takeovers when the alternate CICS is running on a different MVS image by setting the QUIESCE=NO option for SDUMP, using the MVS CHNGDUMP command.

Suppressing system dumps that precede ASRx abends

The MVS system dump data sets can become full with unwanted SDUMPs that precede ASRA, ASRB, and ASRD abends (after either message DFHAP0001 or DFHSR0001).

If CICS storage protection is active, you can suppress the system dumps caused by errors in application programs (after message DFHSR0001), while retaining the dumps caused by errors in CICS code (after message DFHAP0001). To do this, use either a CEMT SET SYDUMPCODE command, or an EXEC CICS SET SYSDUMPCODE command to suppress system dumps for system dumpcode SR0001.

CEMT SET SYDUMPCODE(SR0001) ADD NOSYSDUMP

CICS uses dumpcode SR0001 if an application program was executing in user-key at the time of the program check or MVS abend. This is only possible if storage protection is active. If the program was executing in CICS-key, dumpcode AP0001 is used instead.

Where storage protection is not active, SDUMPs can be suppressed by suppressing dumpcode AP0001. However, note that this suppresses dumps for errors in both application and CICS programs. The XDUREQ Global User Exit can be used to distinguish between AP0001 situations in application and CICS programs.

For more information about the storage protection facilities available in CICS, see Storage protection.

If you want SDUMPs for one of these transaction abends but not the other, select the one you want by using either a CEMT TRDUMPCODE or an EXEC CICS TRANDUMPCODE command. This specifies, on an entry in the dump table, that SDUMPs are to be taken for either ASRA, ASRB, or ASRD abends. For example, specifying:

CEMT SET TRDUMPCODE(ASRB) ADD SYSDUMP

adds an entry to the dump table and ensures that SDUMPs are taken for ASRB abends. However, in this case the SDUMPs are taken at a later point than SDUMPs usually taken for system dump code AP0001 and SR0001.

For information about the DFHAP0001 and DFHSR0001 messages, see the CICS Messages and Codes and the CICS Problem Determination Guide.

Processing system dumps

You can process a system dump using IPCS, either online under TSO, or by submitting a batch job to print it. IPCS is described in the OS/390 MVS IPCS User’s Guide, GC28-1756. For information about the IPCS VERBEXIT parameters that you use with the CICS IPCS dump exit, see the CICS Operations and Utilities Guide.

[[ Contents Previous Page | Next Page Index ]]