Mor(e )on UIC

(Originally posted 2007-10-03.)

Thanks to the people who responded to this blog entry. And to the people who talked to me offline.

The result is a slight shift in emphasis: I never did talk about UIC as the primary metric of memory constraint. If you read the referenced blog item I mentioned it as one of three, alongside paging rate and free frames. The shift is that I’m going to be more strident about UIC in future, relegating it to “third place”…

1. Obviously copious free frames would suggest no constraint.
2. Obviously significant paging would tend to suggest some level of shortage – though customers have been reporting some paging even when there are tons of frames free (and I haven’t had a good explanation for that yet).
3. If UIC is dropping then that ought to be some kind of indicator of constraint.

As always “constraint” has to be seen in the light of goal attainment for important service class periods. You can see “delay for paging” samples in Workload Activity Report.

Did I say I was making this up as I go along? I didn’t? 🙂

Seriously, I’ve yet to see a day’s worth of z/OS R.8 data from a Production system. I expect to any week now. But rest assured, dear reader, if you get to send me such data I’ll be ready for it. 🙂