PM75060: IN DB2 V10 WHEN RUNSTATS OFFLOADS TO ZIIP IT CREATES DEPENDENT WLM ENCLAVES IN STC INSTEAD OF WORK-DEPENDENT ENCLAVES

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APAR status

  • Closed as program error.

Error description

  • In DB2 v10 when Runstats offloads to ZIIP it creates dependent
    WLM enclaves in STC instead of work-dependent enclaves
    This causes a problem for SAP customers who run WLM Enclaves
    and DB2 stored procedures like ADMIN_UTL_SCHEDULE
    In the reported case, a SAP ABAP program calls DB2 stored
    procedure ADMIN_UTL_SCHEDULE with max_parallel 10 and 1000
    tablespaces to process RUNSTATS.
    ADMIN_UTL_SCHEDULE calls up to 10 stored procedures DSNUTILS
    In DB2 9, there is one WLM Enclave for the SAP connection
    which executes ADMIN_UTL_SCHEDULE.
    All CPU time is aggregated into this Enclave, including CPU
    Time of RUNSTATS.
    The WLM Appl Enc Procs D6M0WLMU do not really consume CPU Time.
    In DB2 v10 there is one DDF Enclave for the ABAP connection
    and 10 extra STC Enclaves for each WLM Appl. Env Proc D6Y0WLMU,
    which executes RUNSTATS.
    The RUNSTATS CPU Time is associated to the STC Enclaves and
    not aggregated into the DDF Enclave.
    For SAP workload, customers like this classify DDF only and
    now, with Db2 v10 SAP driven workload appears in STC.
    Unfortunately, their WLM policy maps the extra STC Enclaves
    into STCHIGH, which causes performance problems for the SAP
    dialog users.
    Customers would like this to have a behavior like in DB2 v9.
    

Local fix

Problem summary

  • ****************************************************************
    * USERS AFFECTED: All DB2 10 for z/OS utility users of         *
    *                 utilities that offload to zIIP processors    *
    ****************************************************************
    * PROBLEM DESCRIPTION: RUNSTATS always creates a new enclave   *
    *                      to off-load to zIIP processors instead  *
    *                      of executing in the current one if      *
    *                      already executing in one.               *
    ****************************************************************
    * RECOMMENDATION: Apply corrective PTF when available          *
    ****************************************************************
    When RUNSTATS can off-load to zIIP processors, it creates an
    enclave in which they will run.  When already executing in an
    enclave, it needs to schedule into that enclave.
    
    While this was reported against RUNSTATS, any utility that will
    off-load to the zIIP processors can run into this and should
    continue processing in the current enclave in which it is
    running.
    

Problem conclusion

  • Utilities that off-load work into an enclave will now schedule
    into the enclave it is currently running in.  If it is not, then
    a new enclave will be created for the off-load to run in.
    

Temporary fix

Comments

APAR Information

  • APAR number

    PM75060

  • Reported component name

    DB2 OS/390 & Z/

  • Reported component ID

    5740XYR00

  • Reported release

    A10

  • Status

    CLOSED PER

  • PE

    NoPE

  • HIPER

    NoHIPER

  • Special Attention

    NoSpecatt

  • Submitted date

    2012-10-15

  • Closed date

    2012-12-21

  • Last modified date

    2013-02-04

  • APAR is sysrouted FROM one or more of the following:

  • APAR is sysrouted TO one or more of the following:

    UK90599

Modules/Macros

  •    DSNURBXA DSNURBXC DSNURFBR DSNURSCN DSNUSDRC
    

Fix information

  • Fixed component name

    DB2 OS/390 & Z/

  • Fixed component ID

    5740XYR00

Applicable component levels

  • RA10 PSY UK90599

       UP13/01/10 P F301

Fix is available

  • Select the PTF appropriate for your component level. You will be required to sign in. Distribution on physical media is not available in all countries.



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Document information


More support for:

DB2 for z/OS

Software version:

A10

Reference #:

PM75060

Modified date:

2013-02-04

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