A Region without Storage is like a Car without Fuel... It will not Start
ByronBaldwin 06000099ST Visits (5083)
In today's time, many people are looking for alternative fuel sources to power our vehicles. Without that fuel source our vehicles will not start. This logic works the same for a CICS region.
Short on Storage (SOS) issues when CICS is initializing tend to get a bit more attention because the region is unable to fully initialize. In this blog post I will be discussing this very issue as well as the resolution.
I recently worked on an SOS problem and I wanted to take you through what I found. I was able to see the region was SOS above the line. The EDSA was set to 34M. The ECDSA owns 14M, EUDSA 1M and the ERDSA owns 19M while the ESDSA does not have any storage allocated to it.
The ECDSA shows the following subpool which owns large amounts of storage:
The ERDSA shows the following subpools which own large amounts of storage:
The EDSA Limit of 34M does seem a bit low, but since the client didn't make any changes to the DSA sizes, it makes me hesitant to ask them to increase the EDSA limit. I wanted to investigate this a bit more...
Reviewing the DS (dispatcher) domain it revealed a number of entries in DMWTQUEU type waits but only one of them had a task associated with it (the entries in the DS domain which are in the DMWTQUEU which do not have task associated with them are attempting to run on the CO TCB). That task is CSXM (Task 00003, KE-NUM=0022). The stack for this task appears to be waiting on the RM domain which is currently in a system wait per the DM domain:
0022 18D16020 0120 Bot 96201C00 96201FBC 0003BC DFHKETA
The RM domain showed the following tasks with an INFLIGHT status:
The RM, SO, domain are currently quiesced.
I found the cause of this issue was due to the REGION card on the startup had been changed to 70M from 0M. 0M would allow all the available private storage above and below the 16 MB line to be used. Since CICS was limited to 70M, it obtained as much storage as it could, but it wasn't enough and the region went into a wait for more storage. Once the REGION card was changed back to 0M, the region initialized. REGION=0M might not be the best fit for your environment (your mileage may vary), so you should see the Estimating and setting REGION section in the CICS information center for recommendations.
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 and I will do my best to accommodate the request. As always DO IT JUST FOR CICS!!!