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PM50592: IMPROVING PERFORMANCE FOR SHORT RUNNING PAIR-WISE JOIN QUERY.

A fix is available

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APAR status

  • Closed as program error.

Error description

  • Improving performance for short running pair-wise join query.
    

Local fix

  • n/a
    

Problem summary

  • ****************************************************************
    * USERS AFFECTED: All DB2 for z/OS users utilizing starjoin    *
    *                 pair-wise join technology and                *
    *                 parallelism.                                 *
    ****************************************************************
    * PROBLEM DESCRIPTION: Sometimes a query which should run      *
    *                      in a short amount of time may run       *
    *                      longer when the following conditions    *
    *                      are met.                                *
    *                                                              *
    *                      1. Pairwise join plan is used           *
    *                      2. There is only one pairjoin leg       *
    *                      3. The query is estimated to run in     *
    *                         less than 0.5 sec.                   *
    *                                                              *
    *                      When the conditions above are met,      *
    *                      the query can actually have a longer    *
    *                      elapsed time.                           *
    *                                                              *
    *                      SQLPAIRWISEJOIN SQLSTARJOIN             *
    *                      SQLPERFORMANCE SQLPARALLELISM           *
    *                      PARALLELISM DB2PARALL/K                 *
    ****************************************************************
    * RECOMMENDATION:                                              *
    ****************************************************************
    Sometimes a query that should run in a short amount of time
    may run longer when the following conditions are met.
    
    1. Pairwise join plan is used
    2. There is only one pairjoin leg
    3. The query is estimated to run in less than 0.5 sec.
    
    When a pairjoin plan is being processed, regardless
    of whether the user enables parallelism or not,
    DB2 will always try to activate parallelism to process
    the pairjoin legs.
    
    The problem occurs because of a bug in the time interval
    used for the parent task to wake up and check the child
    task status.
    

Problem conclusion

  • The problem described above is fixed in some cases
    by using a short initial time interval for the
    parent task to wake up and check the status of the
    child task.
    

Temporary fix

Comments

APAR Information

  • APAR number

    PM50592

  • Reported component name

    DB2 OS/390 & Z/

  • Reported component ID

    5740XYR00

  • Reported release

    910

  • Status

    CLOSED PER

  • PE

    NoPE

  • HIPER

    NoHIPER

  • Special Attention

    NoSpecatt

  • Submitted date

    2011-10-20

  • Closed date

    2012-02-15

  • Last modified date

    2012-03-01

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

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

    UK76211 UK76212

Modules/Macros

  •    DSNXGRTS DSNXOGP  DSNXOPJD DSNXROPT DSNXRPJP
    

Fix information

  • Fixed component name

    DB2 OS/390 & Z/

  • Fixed component ID

    5740XYR00

Applicable component levels

  • RA10 PSY UK76211

       UP12/03/01 P F202

  • R910 PSY UK76212

       UP12/03/01 P F202

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.



Document information

More support for: DB2 for z/OS

Software version: 910

Reference #: PM50592

Modified date: 01 March 2012


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