Home > CICSPlex SM, debug, MVS, SLIP > Using MVS SLIP to detect memory changes

Using MVS SLIP to detect memory changes

Every now and then you come across a problem that you just can’t fix with the tools in your toolbelt. The problem? How to detect what part of your program is changing a specific area of storage? The program in question being CICSPlex SM and the storage a 1 byte flag stored in a MVS dataspace. A code search only proved that the flag was not being modified anywhere obvious and a trace of the suspect modules proved unhelpful.

So failing to batter the problem into submission with the normal tools, a kind colleague pointed me at the MVS SLIP (Serviceability Level Indication Processing) operator command. A few painful moments passed as the correct command incantation was established and lo and behold I received a dump with the PSW pointing handily at the module that changed the storage location. Thankfully we use eye-catchers at the top of each internal method so detecting the module is simply a matter of browsing the dump at the address suggested and scrolling up.

Generally within the CICS TS team the most commonly used tools for debugging problems are CEMT, CECI, IPCS, AUX trace and an internal interactive debugging tool called Source Language Debug (SLD). In CICSPlex SM development/service we also use the customer-provided COD0 transaction to quickly walk-around the system control blocks and dump out specific data.

The SLIP command is definitely one tool I’ll be adding to my toolbelt. What tools can you not live without?

Categories: CICSPlex SM, debug, MVS, SLIP
  1. Grant
    May 8, 2008 at 6:34 pm

    Well, developers of CICS (as opposed to CICS application developers) have a different toolbag, so other tools I have used in the past (when I was a real CICS sysprog) are Intertest for CICS, CEDF, CSFE, TMON Supertrace to name but a few.

    For CICS support work, DFHTRAP can be a godsend – though strangely with CICSPlex SM support work, I’ve never come across the time when I’ve found the need a CICSPlex SM equivalent. Another handy CICSPlex SM related tools are COLU and EYU9XENF.

    Of course there is Debug Tool, and the support for remote debugging via Rational Developer for System z.

  1. May 21, 2008 at 8:57 pm

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