Some WLM Questions

(Originally posted 2015-01-10.)

As I’m working with a couple of colleagues on a performance study I thought I’d list some “starter set” questions I’d ask about any customer’s WLM policy.[1]

Before you go too far with this post you might like to read Analysing A WLM Policy – Part 1 and Analysing A WLM Policy – Part 2 but I don’t think I’m repeating myself much here.

So here are some key questions I can seek to answer:

  • Does the policy have a reasonable Importance distribution, CPU-wise?[2]
  • Is work appropriately classified?[3]
  • Are Importance 1 goals met barely, easily, or not at all?
    • How do they bear up with load?
    • Which components of Using and Delay feature most highly?
  • Are Importance 2 goal met barely, easily, or not at all?[4]
  • Do transaction-based goals have the right kind of period structure?
  • Does the policy have a proliferation of active service class periods?
  • Is there a sensible separation between velocity levels?[5]
  • Are policies enabled effectively?[6]
  • How are Report Classes used?

Many of you, I’m quite sure, are capable of answering all these questions – based on your analysis of your own data. But certainly these are questions I’m likely to address if you’re one of the customers I’m lucky enough to deal with.[7] Indeed I wrote a slide of questions – you might see – in parallel with writing this post.

Food for thought? 🙂

And one final thought: There’s a question I can’t directly answer but would work with any customer of mine on:

  • How do the goals relate to business goals? For example, “where did this Response Time goal come from?”

  1. As it’s a starter set it’s not all the questions you’d ever want to ask; In particular additional lines of enquiry come up while looking at the data and answering these questions.  ↩

  2. If everything’s at Importance 1 there’s little work that can be displaced “when push comes to shove” so extra caution is required, capacitywise.  ↩

  3. For example DB2 DBM1, as mentioned in zIIP Address Space Instrumentation and further discussed in DB2 and Workload Manager – GSE UK Conference  ↩

  4. I’m tempted to write “and so on” here but I think Importance 3 and below probably need a graduatedly decreasing level of scrutiny.  ↩

  5. See WLM Velocity – Another Fine Rhetorical Device I’ve Gotten Myself Into  ↩

  6. For example Day and Night policies making sense.  ↩

  7. Its a bit of a wake up call that formulating this set of questions leads me to the conclusion that on a big study our reporting isn’t particularly efficient in answering some of these – though our reports do answer a lot of these questions, with some specialist time being burnt. More development work to do… 🙂  ↩

Published by Martin Packer

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