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Sometimes it is desirable to get information about the contents of registers or data areas for a program that is not behaving as expected without altering or interrupting the operation of that program. The SLIP subcommand of OPER can be used to collect this information. The following SLIP command: SLIP SET,IF,ID=xxxx,A=TRACE,TRDATA=(STD,REGS),J=jobname,PVTMOD=(pgm,start,end),END will trace activity in the specified program (pgm) between offsets "start" and "end" for job, user or started task "jobname". An entry is to be created for each instruction fetch (IF) which matches the specified criteria. You want to be as specific as possible to avoid introducing unnecessary overhead into your system. For each matching event, an entry will be creating containing a standard header and register contents.

The SLIP command supports other selection criteria for specifying which events should be monitored and what data should be collected. For example, you can specify that the contents of an area pointed to by the contents of a specified register be captured for each matching event. Refer to the "MVS System Commands" publication or the "Service Aids" publication for more details.

To collect this information, you need to have GTF running specifying a parm member similar to the following:

TRACE=SLIP GTF is started using an operator command similar to the following: S GTF.GTF,MEMBER=parm,DSN=tracedsn GTF will at this point normally issue a message like: xx AHL125A RESPECIFY TRACE OPTIONS OR REPLY U Respond with the operator command R xx,U to continue. Once the activity that you wanted to monitor has completed, enter P GTF to stop GTF. Enter the command SLIP DEL,ID=xxxx to remove your slip.The procedure used to start GTF may vary depending on your installation's procedures.

You can check out the contents of your trace using IPCS. You can either use the GTFTRACE command of IPCS or use the IPCS panels for formatting trace output, using the dataset name specified to GTF earlier as input.

For more information, refer to the "Service Aids" publication associated with your release of MVS.


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