PM75473: DDF THREADS INTERMITTENTLY TOOK MORE THAN 20 SECONDS TO FINISH. HIGH STORAGE MGR LATCH CONTENTION. ABENDS RC00E20003, RC00E20016

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APAR status

  • Closed as program error.

Error description

  • DB2DDF Defect pm75473 dpm75473
    DDF threads would slow down intermittently and took more than
    20 seconds to finish whereas usually it took less than one
    second to finish.  The incoming DDF threads were queued due to
    the slow down and then soon MAXDBAT was reached. Then the
    storage shortage abends 00E20003 or 00E20016 occurred.
    ***********************************************************
    Additional Symptoms and Keywords:
     Short On Storage SOS Performance PERF LCBLSTKP
     ABEND04E AB04E S004E 04E
      04E-00E20003 00E20003 RC00E20003
       DSNGEPLC DSNSVBK  DSNGEPLC.DSNSVBK +05EA
       DSNXEPM  DSNSVBK  DSNXEPM .DSNSVBK +05EA
       DSNXOTDA DSNSVBK  DSNXOTDA.DSNSVBK +05EA
      04E-00E20016 00E20016 RC00E20016
       DSNSLD1  DSNSVSTK DSNSLD1 .DSNSVSTK+0656
    

Local fix

Problem summary

  • ****************************************************************
    * USERS AFFECTED: All Distributed Data Facility (DDF) users.   *
    ****************************************************************
    * PROBLEM DESCRIPTION: Intermittent performance problems may   *
    *                      be observed due to contention related   *
    *                      to DDF communication buffer storage     *
    *                      usage.                                  *
    *                      Unpredictable, storage related, abends  *
    *                      may also occur. Symptoms may include:   *
    *                      . ABND=04E-00E20003,                    *
    *                        LOC=DSNGEPLC.DSNSVBK +05EA            *
    *                      . ABND=04E-00E20003,                    *
    *                        LOC=DSNXEPM .DSNSVBK +05EA            *
    *                      . ABND=04E-00E20016,                    *
    *                        LOC=DSNSLD1 .DSNSVSTK+0656            *
    *                      . ABND=04E-00E20003,                    *
    *                        LOC=DSNXOTDA.DSNSVBK +05EA            *
    ****************************************************************
    * RECOMMENDATION:                                              *
    ****************************************************************
    To satisfy remote application SQL activity, distributed server
    threads may acquire vast amounts of 64-bit shared private
    (communication buffer) storage.  As storage utilization
    increases, delays of 20 seconds or more may occur when
    satisfying storage requests from a storage pool which has a
    limited number of extra blocks allowed by its definition.
    This may lead to application/transaction delays and/or storage
    related abends.
    

Problem conclusion

  • DDF initialization has been changed to increase the number of
    extra blocks allowed to satisfy a get storage request to match
    the number of blocks that are actually requested at a time.
    This reduces the number of storage scans and expansions
    necessary to satisfy a "get storage" request thereby reducing
    latch contention.  This allows threads to get and release
    storage more quickly which minimizes abends due to storage
    shortage.  This leads to an improvement in overall DDF
    transaction response time.
    

Temporary fix

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

Comments

APAR Information

  • APAR number

    PM75473

  • Reported component name

    DB2 OS/390 & Z/

  • Reported component ID

    5740XYR00

  • Reported release

    910

  • Status

    CLOSED PER

  • PE

    NoPE

  • HIPER

    YesHIPER

  • Special Attention

    NoSpecatt

  • Submitted date

    2012-10-19

  • Closed date

    2013-01-24

  • Last modified date

    2013-03-04

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

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

    UK91168 UK91169

Modules/Macros

  •    DSNLIINI
    

Fix information

  • Fixed component name

    DB2 OS/390 & Z/

  • Fixed component ID

    5740XYR00

Applicable component levels

  • RA10 PSY UK91168

       UP13/02/09 P F302

  • R910 PSY UK91169

       UP13/02/09 P F302

Fix is available

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Document information


More support for:

DB2 for z/OS

Software version:

910

Reference #:

PM75473

Modified date:

2013-03-04

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