PM91205: INEFFICIENT ACCESS PATH FOR A SUBQUERY

A fix is available

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You can track all active APARs for this component.

APAR status

  • Closed as program error.

Error description

  • When DB2 is considering correlated options for a subquery,
    several variables are not properly initialized.  Depending on
    the pre-existing values these variables obtain from storage,
    this may result in a inefficient access path for the correlated
    subquery.  This problem only occurs with OPTXQB=ON.
    
    SQLPERFORMANCE SQLACCESSPATH
    

Local fix

  • Optimization hint.
    

Problem summary

  • ****************************************************************
    * USERS AFFECTED: DB2 9 for z/OS users with queries containing *
    *                 subqueries.                                  *
    ****************************************************************
    * PROBLEM DESCRIPTION: DB2 may select an inefficient access    *
    *                      path for a subquery when zparm OPTXQB   *
    *                      is set to ON.                           *
    ****************************************************************
    * RECOMMENDATION:                                              *
    ****************************************************************
    When zparm OPTXQB=ON, DB2 can incorrectly reference an
    uninitialized variable when determining the cost of a subquery.
    This problem may result in an inefficient access path.
    
    Note that this problem may be intermittent depending on the
    contents of the storage occupied by the uninitialized variable.
    
    Additional keywords:
    SQLPERFORMANCE SQLACCESSPATH SQLSUBQUERY SQLNONCORRSUBQ
    SQLCORRSUBQ
    

Problem conclusion

  • DB2 code has been modified to properly initialize the variable.
    

Temporary fix

Comments

APAR Information

  • APAR number

    PM91205

  • 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

    2013-06-17

  • Closed date

    2013-10-10

  • Last modified date

    2013-11-04

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

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

    UK98285

Modules/Macros

  •    DSNXOGCX
    

Fix information

  • Fixed component name

    DB2 OS/390 & Z/

  • Fixed component ID

    5740XYR00

Applicable component levels

  • R910 PSY UK98285

       UP13/10/25 P F310

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:

910

Reference #:

PM91205

Modified date:

2013-11-04

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