Mainframe, Performance, Topics Podcast

Episode 15 "Waits and Measures"

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Here are the show notes for Episode 15 "Waits and Measures". The show is called this because our Performance topic is about LPAR weights, and because this episode was after a seasonal hiatus.

Mainframe

Our "Mainframe" topic discusses a small new function in z/OS UNIX V2.3: automatic unmount of the version "root" file system in a shared file system environment. Our guest was Barry Lichtenstein, the developer of the function, and he told us all about it:

  • there is a new BPXPRMxx VERSION statement parameter, UNMOUNT. This means that when no one is using that "version filesystem", it will be automatically unmounted. This is not the default. Syntax here
  • this function is nice, as it will allow an unused version file system to be "rolled off" when you don't need it anymore. Unused here, means that no system is using it or using any file system mounted under it. z/OS UNIX will do this detection automatically, and unmount not just the version file system, but mounted file systems under it that are no longer used by any systems after an unspecified amount of time.
  • you can turn this on and off dynamically with a SET OMVS or SETOMVS command. There is DISPLAY command support of it. And perhaps the best news, the health check USS_PARMLIB will see if the current settings don't match the used parmlib specification. 
  • we weren't sure if SMF record 92 would be cut when the unmount happened, but Barry said nothing unique was happening for this function so what happens today is most likely the same behavior. There are messages that are issued in the hardcopy log when the unmounts happen. SMF 90 might be issued for SET changes.
    • Performance

    Martin talked about Weights and Online Engines in LPARs, and Martin again looking at customer information.

    • Intelligent Resource Director (IRD) changed PR/SM worked:
      1. Dynamic weight adjustment
      2. Online logical engine management (vary online and offline). Shows minimum and maximum weights when changed by IRD.
      3. HiperDispatch: took away logical engine management (and manages it better!), and kept IRD dynamic weight adjustment. With HiperDispatch's parking of engines, no work is directed towards it. 
      4. More instrumentation was introduced, such as Parked Time and refined instrumentation on weights (vertical weights, by engine).
      5. Customer situation was that they did their own version of IRD and HiperDispatch: Varying logical engines online and varying weights (not using IRD itself). Martin expected IRD to change weights, but he saw the IRD weight fields were all zero. 
      6. Why not let IRD do it? Martin thinks there was something in the customer's mind to control it themselves.
      7. Why not use HiperDispatch? Martin thinks that maybe a subtle difference might be needed, but LPARs should be designed properly. 
        8. Topics

        Our podcast "Topics" topic was "Video Killed the Radio Star?" and about screencasting.  Martin has been trying to post screencasts to YouTube. Here's one.

        Contacting Us

        You can reach Marna on Twitter as mwalle and by email.

        You can reach Martin on Twitter as martinpacker and by email and blogs at blog.

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        Mainframe, Performance, Topics PodcastBy Marna Walle