Q

Questions about CICS Short-on-Storage processing

I'm an SP in OS/390. Recently, our CICS (Version CICS TS 1.3) keep on showing "short on storage (below 16M)". Whenever this happen, many VSAM files' AIX would be corrupted!

Our CICS SP was failed to adjust the DSA in CICS system definition. And I'm trying to assist him to review all the setting in CICS resource definition.

I would like to know, how would the CICS release storage when it is in SOS? How CICS controls all the VSAM files I/O buffer? Is there any relationship between the "short on storage" and the corruption of online VSAM files?

First let me say that CICS Short-on-Storage processing should not, under any circumstances, cause loss of data integrity.

To answer your specific question, when CICS goes SOS it will:
-Throttle new work coming into the system, to prevent matters getting any worse -Perform program compression, freeing inactive programs -Free inactive buffers (note VSAM buffers are above the 16MB line) -Reduce priority of recently attached tasks, to allow transactions nearing completion to terminate and free their storage

There should be no relationship between SOS and corruption of online VSAM files. I assume CICS recovered from the stress situation and continued normally. If CICS crashed because it was not able to recover from the SOS condition, I assume you performed an emergency restart to allow in-flight data updates to be backed-out.

This was first published in May 2002

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