Mainframe, Performance, Topics Podcast

Episode 10 "234U"

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Here are the show notes for Episode 10 "234U". The show is called "234U" because:

  • We are very happy that we can talk about z/OS V2.3 now that it's been previewed on February 21, 2017.
  • We liked the consecutiveness 2-3-4, and U added works nicely.
    • Mainframe

    Our "Mainframe" topic was a highlight of some of the newly previewed z/OS V2.3 enhancements! We will surely talk a lot about z/OS V2.3 in podcasts to come.

    First, it is important to know that z/OS V2.3 will only IPL on an zEC12, zBC12 and higher. Prepare now if you need to.

    Here's a brief list of the items planned for V2.3 (which is planned to GA on September 29, 2017)

    • System logger's log stream staging datasets can be allocated greater than 4 gigabytes.
    • Data set encryption for z/OS data sets and zFS file systems (policy-enabled), and CF structures (list and cache, with the CFRM policy).
    • zFS:
    • zEDC compression on individual files, and existing and new zFS files systems. Existing zFS while in use!
    • Salvage utility to run online with file system is still mounted
    • Dynamic changes to aggregrate attributes for common MOUNT options, and dynamic changes to sysplex sharing status.
    • New facility (from TSO or UNIX shell) to allow for migration from HFS to zFS, without requiring the "from" file system to be unmounted.
    • email: ability to have an email address in the RACF user profile. JES2 and z/OSMF could use email notification to the user.
    • JES2 JCL, the delimiter keyword (DLM) on SYSIN is extended from 2 to 18 characters long.
    • SCRT is a component delivered in z/OS, with support for enabling ISVs to generate an ISV-unique SCRT report.
    • Auto-starting z/OSMF be default, late in the IPL hopefully after OMVS and TCP/IP are up. The biggest migration action in z/OS V2.3 identified yet.
    • TSO/E support for 8 character userids. Many products require changes to support this, so do planning for this one.


      • Performance

      Martin had an esteemed guest for our "Performance" topic, Elpida Tzortzatos, Distinquished Engineer from z/OS Development.

      Martin and Elpida chatted about several important recent advances made in the area of z/OS memory management.

      • Review of UIC (Unreferenced Interval Count), which is how long in seconds

        • a page has remained unreferenced. High count is low contention, low count is high contention. Since moving to large memory (64-bit, zArch), the design changed to reduce the review frequency from 1 sec to 10 seconds.

        When more memory support was added (128G to 4TB) it was again reduced to not do any UIC updates, other metrics are used to judge contention instead.

        • RMF reports high impact, medium impact, and low impact frames evicted today, for a performance judgement.

        Customers should be looking at average available memory, and minimum too. Make sure your AFQ can handle workload spikes and SVC dumps. Here is a WSC paper about that.

      • Large frames (1MB and 2GB page sizes): the Dynamic Address Translation (DAT) is on the critical performance path

        • Use the LFAREA specification for 1MB and 2GB frame usage.

        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