Plan Your ESQA Carefully For z/OS Release 11

(Originally posted 2009-11-30.)

Thanks to Marna Walle for pointing out this change:

In z/OS Release 11 there is a requirement for an additional 1608 bytes of ESQA per address space. To put that in context, I’ll do some obvious maths: That’s about 1.6MB per 1000 address spaces. It just might be of interest to certain customers I know with thousands of CICS regions in a system, or very large TSO or Batch systems. It’s probably not enough to trouble most people. But it reminds me of the importance of having a quick virtual storage check when migrating from one major product release to another.

There are several ways of checking for this particular one:

• You can use Healthchecker VSM_SQA_THRESHOLD check.
• You can process the SMF 78-2 Virtual Storage record.

The latter would be my favourite as using the SMF 78-2 data to look at usage by time of day can show some useful patterns. You might want to review, for example, whether (E)SQA threatens to overlow into (E)CSA. It’s not a big tragedy if that happens but your installation might have views on such things.

(In case you’re unfamiliar with such things the “E” in “(E)SQA” and “(E)CSA” refers to 31-bit areas whereas the names without the “E” refer to 24-bit areas, there being analogues above and below the line for both SQA and CSA.)

One other thing – in case you think ESQA and ECSA are unimportant having very large such areas can impact on the 31-bit Private Area virtual storage picture.