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PH00318: UNEXPECTED HIGH CPU CONSUMED WHEN QUERY ON COMPRESSED TABLE IN SELECT LIST AND PREDICATIONMNS

A fix is available

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APAR status

  • Closed as program error.

Error description

  • Unexpected high CPU consumed when query on compressed table
    space and contains partly columns in select list and predication
    

Local fix

  • n/a
    

Problem summary

  • ****************************************************************
    * USERS AFFECTED: All Db2 for z/OS users using Db2 to compress *
    *                 and decompress data.                         *
    ****************************************************************
    * PROBLEM DESCRIPTION: When Db2 data is compressed, a query    *
    *                      with a short selection list may have    *
    *                      a higher CPU consumption than a         *
    *                      longer selection list.                  *
    ****************************************************************
    * RECOMMENDATION: Apply corrective PTF when available.         *
    ****************************************************************
    When Db2 calculates the decompression cost for a query that
    uses table space scan access, Db2 compares the cost between a
    partial decompression and a full decompression of a merged
    set of columns, the optimization logic incorrectly picks a more
    expensive decompression method. This may lead to an increase
    in CPU usage.
    

Problem conclusion

  • Db2 decompression optimization logic has been fixed to
    correctly choose the least expensive decompression method.
    

Temporary fix

Comments

APAR Information

  • APAR number

    PH00318

  • Reported component name

    DB2 OS/390 & Z/

  • Reported component ID

    5740XYR00

  • Reported release

    B10

  • Status

    CLOSED PER

  • PE

    NoPE

  • HIPER

    NoHIPER

  • Special Attention

    NoSpecatt / Xsystem

  • Submitted date

    2018-07-11

  • Closed date

    2018-08-20

  • Last modified date

    2018-10-02

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

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

    UI57966 UI57967

Modules/Macros

  •    DSNIIMSI
    

Fix information

  • Fixed component name

    DB2 OS/390 & Z/

  • Fixed component ID

    5740XYR00

Applicable component levels

  • RB10 PSY UI57967

       UP18/09/05 P F809

  • RC10 PSY UI57966

       UP18/09/05 P F809

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: 11.0

Reference #: PH00318

Modified date: 02 October 2018


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