CICS Dumps unusable due to Storage Overlay
ByronBaldwin 06000099ST Visits (6487)
As a level II representative for CICS our ability to provide accurate resolutions to client problems relies heavily on the documentation (dumps, logs, traces) captured at the time the situation is occurring. When that documentation is not available or unusable (in this case) then level II representatives have to search for alternative ways to investigate the issue. I wanted to talk about one such case; thankfully the reported issue had a resolution in place.
During a recent issue a client stated their CICS region was hung and prior to canceling the region, the client captured an SVC dump. Upon sending the dump in for review it was initially thought the dump was unusable. When support attempted to format the dump for review they received the following messages:
DFHPD0129 CICS Domain Anchor Blocks not found for AFCB. Scan will continue.
From time to time we see the aforementioned messages if there was a problem in the transmission of the dump using the FTP process. We sometimes ask the client to resend the dump for review. The majority of the time this action would correct the problem, but not in this case. While attempting to resolve the problem with the documentation the client was still encountering the problem.
At this point we asked the client if they are able to use IPCS on their system to format the dump. They stated they are able to format the dumps only if they do not encounter the 0C4 abend (Lightbulb moment). At this point, we investigated the log and located the abend 0C4. This abend was being reported by message IEA995I. The 0C4 was occurring in DFHKERER. The module was failing repeatedly trying to record the errors. However, the Kernel anchor block (KCB) had been overlaid with the DFHAP1301 parameter list. If you run into this problem, the overlay can be verified in the dump by locating the KCB, which is generally located at address 7000 in the dump, but if it looks like the following it shows the DFHAP1301 parameter list not the KCB:
00007000 00F80000 00000026 00000001 00000000 00007010 B4800200 00000000 01000000 00000000 00007020 00000000 00000515 00000000 00000000
This is a known issue and it has been addressed with a HIPER APAR and PTF depending on your version of CICS Transaction Server for z/OS (CICS TS):
Please apply this HIPER fix top your system to ensure this problem does not occur in your region.
As always I would love to hear your feedback concerning this blog entry. If you have topics you would like to hear about please feel free to advise as well and I will do my best to accommodate the request. As always DO IT JUST FOR CICS!!!