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PK56337: PRE-CONDITIONING APAR FOR APAR PK66539.

A fix is available

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APAR status

  • Closed as program error.

Error description

  • Poor performance from XPath expression with parent axis.
    (PK56337 is the pre-conditioning apar for PK66539).
    

Local fix

Problem summary

  • ****************************************************************
    * USERS AFFECTED: DB2 R910 Users who use XMLQuery/XMLTable/    *
    *                 XMLExists with multiple parent-axis steps    *
    *                 (e.g., ../..)                                *
    ****************************************************************
    * PROBLEM DESCRIPTION: PRECONDITIONING APAR to improve the     *
    *                      performance of XMLQuery/XMLTable/       *
    *                      XMLExists (especially XMLTable) with    *
    *                      multiple parent-axis steps (e.g.,       *
    *                      ../..) in terms of CPU time and         *
    *                      storage usage.                          *
    ****************************************************************
    * RECOMMENDATION:                                              *
    ****************************************************************
    The performance of XMLQuery/XMLTable/XMLExists (especially
    XMLTable) with multiple parent-axis steps (e.g., ../..) needs
    to be enhanced to avoid multiple scans and extensive usage of
    storage. PK56337 and PK66539 help to achieve that. PK56337 is
    the preconditioning APAR.
    
    For example:
    
    The following query uses parent-axis in column definitions of
    an XMLTable.
    
    SELECT X.*
        FROM ADMF001.STATE_XML,
             XMLTABLE('/doc/state/college/students/student/classes
                       /class'
             PASSING STATE_COLLEGE
             COLUMNS
               "STATEID"   INTEGER path '../../../../../@stateid',
               "COLLEGEID" BIGINT  path '../../../../@id',
               "TEACHERID" INTEGER path '@teacherid',
               "STUDENTID" INTEGER path '../../@studentid',
               "COURSEID"  SMALLINT path '@courseid',
               "GRADE"     DECIMAL path '@grade',
               "SEMESTER"  DATE path '@semester'
             ) AS X;
    
    In this query, there are multiple parent-axis steps in some
    column definitions. The query execution is both time and space
    consuming because it requires to perform multiple get-parent
    scans to retrieve the ancestor node and needs to do this
    repeatedly for all the rows in XMLTable.
    

Problem conclusion

  • PK56337 is the preconditioning APAR and PK66539 is the enabling
    APAR for improving the performance of XMLQuery/XMLTable/
    XMLExists (especially XMLTable) with multiple parent-axis steps
    (e.g., ../..). They employ an ancestor node cache and support
    finding ancestor node in one scan. PK56337 should be applied
    before PK66539.
    

Temporary fix

Comments

APAR Information

  • APAR number

    PK56337

  • 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

    2007-11-09

  • Closed date

    2008-07-23

  • Last modified date

    2008-09-02

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

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

    UK38379

Modules/Macros

  • DSNDSXT  DSNNCTIB DSNNOCCN DSNNOGET DSNNOINS
    DSNNORSQ DSNNOSMS DSNNOTTS DSNNQOP  DSNNQSCN DSNNQXCA DSNXMLSM
    

Fix information

  • Fixed component name

    DB2 OS/390 & Z/

  • Fixed component ID

    5740XYR00

Applicable component levels

  • R910 PSY UK38379

       UP08/08/15 P F808

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

Modified date:
02 September 2008