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PI06926: SLOW PERFORMANCE IN CONSECUTIVE INSERT ON UTS BECAUSE DB2 TRIES TO FIND SPACE FROM THE 1ST SPACE MAP PAGE EVERY INSERT.

A fix is available

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APAR status

  • Closed as program error.

Error description

  • Slow performance in consecutive INSERT including Multiple Row
    INSERT on UTS because the last used segment is not updated and
    DB2 tries to find space from the first space map page every
    insert after seeing the last segment full.
     On header page, HPGS1LSG points to the last segment 71BA in
    DSSIZE 4G case (HPGS1LSG='000071BA'X) and the last segment 71BA
    on page FF525 is full like the following:
    *
    PAGE: # 000FF525 -----------------------------------------------
    SEGMENTED SPACEMAP PAGE:  PGCOMB='10'X  PGLOGRBA='CC4383EFD082'X
                              PGNUM='000FF525'X  PGFLAGS='30'X
                              SEGNUM='0046'X  SEGFREE='0000'X
                              SEGENT='0001'X  SEGSIZE='0024'X
                              SEGLENT='000009D8'X  FOEND='N'
    
    
    FIRST PART OF SEGMENTED SPACE MAP:
    SEG 0001   0000717600C680 333333333333333333333333333333333333
    SEG 0002   0000717700C680 333333333333333333333333333333333333
    ...
    SEG 0044   000071B900C680 333333333333333333333333333333333333
    SEG 0045   000071BA00C680 333333333333333333333333333333333333
    SEG 0046   0000000000C680 FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF
    

Local fix

Problem summary

  • ****************************************************************
    * USERS AFFECTED: All DB2 9 for z/OS NFM users who perform     *
    *                 insert operations on Universal Table         *
    *                 spaces.                                      *
    ****************************************************************
    * PROBLEM DESCRIPTION: Insert performance degradation with     *
    *                      high get page count when using          *
    *                      Multi-row insert operation.             *
    ****************************************************************
    * RECOMMENDATION:                                              *
    ****************************************************************
    During the exhaustive search prior to the physical extend of
    the data set, the Multi-Row insert operation encounters a high
    get page count. In this case, insert operation fails to find
    available space to insert and will search the same set of
    space map pages or data pages for each insert operation within
    the same Muli-Row insert statement.
    As a result, a high get page count occurs
    for each Multi-Row Insert statement.
    

Problem conclusion

  • During the exhaustive search step within each Multi-Row insert
    statement, the insert operation will remembered the last
    inserted position. So the subsequent insert operation within
    the same statement will use the prior position as the starting
    point for exhaustive search.
    

Temporary fix

Comments

APAR Information

  • APAR number

    PI06926

  • 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

    2013-11-25

  • Closed date

    2014-04-30

  • Last modified date

    2014-06-03

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

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

    UI17581

Modules/Macros

  • DSNICUBC DSNISGSC DSNISRTI
    

Fix information

  • Fixed component name

    DB2 OS/390 & Z/

  • Fixed component ID

    5740XYR00

Applicable component levels

  • R910 PSY UI17581

       UP14/05/25 P F405

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:
03 June 2014