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PI07513: POSSIBLE HIGH OTHER WRITE I/O FOR INSERT WHEN GBP-DEPENDENT

A fix is available

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APAR status

  • Closed as program error.

Error description

  • Possible high other write I/O for insert or other sql update the
    page when the object is GBP-dependent. There is higher chance
    when uses MEMBER CLUSTER. In some case, OTHER WRITE I/O is
    possibly reported as OTHER READ I/O incorrectly.
    

Local fix

  • Remove the GBP-dependency might could help.
    

Problem summary

  • ****************************************************************
    * USERS AFFECTED: DB2 data sharing users.                      *
    ****************************************************************
    * PROBLEM DESCRIPTION: Performance degradation in data         *
    *                      sharing, most noticeable with INSERT    *
    *                      processing for MEMBER CLUSTER           *
    *                      tablespaces.                            *
    *                                                              *
    *                      Performance is degraded due to hitting  *
    *                      the Vertical Deferred Write Threshold   *
    *                      (VDWQT) too frequently, causing the     *
    *                      INSERT processing to be slowed down by  *
    *                      I/O waits.                              *
    ****************************************************************
    * RECOMMENDATION:                                              *
    ****************************************************************
    For DB2 V10, pages in GBP-dependent pagesets for which an X-mode
    page P-lock is held will be left on the Vertical Deferred Write
    Queue if the P-lock is kept after the page has been written.
    This is commonly done for spacemap pages in MEMBER CLUSTER table
    spaces.  The presence of these pages on the VDWQ can cause
    writes to be scheduled more frequently due to the VDWQT being
    hit.  However, the pages are not modified and so will not be
    written or removed from the VDWQ.  This results is writes being
    scheduled frequently, in which only one or a few pages will be
    written.  And since the pages currently being updated are
    likely to be written, the updating application may be slowed
    down by "other I/O" waits.
    

Problem conclusion

  • The logic which checks for the Vertical Deferred Write Queue
    Threshold being hit has been modified.  It will now consider
    only modified pages, so as not to trigger writes inappropriately
    when few updated pages exist.
    

Temporary fix

  • *********
    * HIPER *
    *********
    

Comments

APAR Information

  • APAR number

    PI07513

  • Reported component name

    DB2 OS/390 & Z/

  • Reported component ID

    5740XYR00

  • Reported release

    A10

  • Status

    CLOSED PER

  • PE

    NoPE

  • HIPER

    YesHIPER

  • Special Attention

    NoSpecatt

  • Submitted date

    2013-12-05

  • Closed date

    2014-02-24

  • Last modified date

    2014-04-02

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

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

    UI15429 UI15430

Modules/Macros

  • DSNB1CMS DSNB1LTS DSNB1LTX DSNB1SWS
    

Fix information

  • Fixed component name

    DB2 OS/390 & Z/

  • Fixed component ID

    5740XYR00

Applicable component levels

  • RA10 PSY UI15429

       UP14/03/12 P F403 ½

  • RB10 PSY UI15430

       UP14/03/12 P F403 ½

Fix is available

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Document Information

Modified date:
02 April 2014