(Originally posted 2013-05-22.)
It’s possible I’ve written something about this before: My blog is so extensive now it’s hard to find out exactly what I’ve written about (and I’m going to have to do something about that).
I say “written something” because I know for sure I haven’t written about the SMF record field I want to introduce you to now.
If when you send me data you include Type 30 interval records I’ll use them to relate WLM Service Classes to Report Classes: Workload, Service Class and Report Class are all in there.
But these records are only for address spaces. Address spaces that actually got created. And therein lies a problem: Only some of the Service Class / Report Class relationships can be gleaned this way.
In practice I’ve found this (incomplete but not inaccurate) information handy. So I’d like to fill in some gaps.
I expect you didn’t know this either – so I call it “new news”: There’s a handy field in SMF 72 Subtype 3 (Workload Activity Report) called R723PLSC. It has nothing to do with PSLC.
This is defined as the “Service Class that last contributed to this Report Class period during this interval.” I’ve highlighted the word “last” as its quite important but we’ll come back to that in a minute.
This allows you to see some relationships for work that isn’t represented by address spaces, for instance DDF. (In my test data it’s DDF I’m seeing.)
I’ve spent some time adding this in to my code. Usually I’d summarise over several hours. In this case if I do I miss stuff.
The emphasised “last” above means that only one of the (potentially several) Service Classes that correspond to this Report Class shows up in the record. So I use a set of rows, each representing a short interval, to get the correspondence. In my test data this approach yields more correspondences – as somehow the last one often isn’t always the same one from interval to interval.
If you use Report Classes to break out a subset of a Service Class the “last Service Class” issue doesn’t arise. If you use Report Classes for aggregation (or in a hybrid way) it certainly does.
(I’m not all that keen on using Report Classes for aggregation anyway: Decent reporting tools can do that for you. But I could be persuaded. I’m keener on using them for breakouts, such as DDF applications that share a common Service Class, or to break out an address space or several.)
I’m not claiming to have got all the Service Class / Report Class correspondences but I’ve got more of them – and for an important set of cases: Service Classes and Report Classes that don’t correspond to address spaces.
As you’ll see in Playing Spot The Difference With WLM Service Definitions I prefer to have the WLM Service Definition to work with – and I’ll be asking for it more fervently in the future. But you have to work with the data you can readily obtain. And R723PLSC is a handy field to have learnt about. You might find it useful, too.