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IC80305: PERFORMANCE DEGRADATION CAUSED BY LATCH CONTENTION ON SQLO_LT_SQLP_DBCB__HEADLSNSEM.

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APAR status

  • Closed as program error.

Error description

  • In high workload circumstance, i.e. many concurrent transaction
    commit, there might be many EDUs waiting for latch
    SQLO_LT_SQLP_DBCB__headLsnSem in following stacks.
    
      sqloXlatchConflict
      sqloXlatchConflict
      sqlpUpdateMinBuffLsn
      sqlpUpdateLowTran
      sqlpScanFirstLsoArrayForLowTran
      sqlpEndUowRuntime
      sqlpxcm1
      sqlrrcom_dps
      sqlrrcom
      sqlrr_commit
      sqljs_ddm_rdbcmm
      sqljsParseRdbAccessed
    
    The stack trace might vary. But, due to the heavy latch
    contention on headLsnSem, the performance will be impacted
    significantly.
    
    The fix for this APAR will reduce the latch contention on
    SQLO_LT_SQLP_DBCB__headLsnSem.
    

Local fix

  • To reduce the chance of hitting this problem, following methods
    can help increase the frequency of flushing dirty pages.
     - set db cfg parameter SOFTMAX to a small value less than 100,
    eg. SOFTMAX=25.
     - specify separated buffer pool for different temp tablespaces.
    

Problem summary

  • ****************************************************************
    * USERS AFFECTED:                                              *
    * All.                                                         *
    ****************************************************************
    * PROBLEM DESCRIPTION:                                         *
    * In high workload circumstance, i.e. many concurrent          *
    * transaction commit, there might be many EDUs waiting for     *
    * latch SQLO_LT_SQLP_DBCB__headLsnSem in following stacks.     *
    *                                                              *
    *   sqloXlatchConflict                                         *
    *   sqloXlatchConflict                                         *
    *   sqlpUpdateMinBuffLsn                                       *
    *   sqlpUpdateLowTran                                          *
    *   sqlpScanFirstLsoArrayForLowTran                            *
    *   sqlpEndUowRuntime                                          *
    *   sqlpxcm1                                                   *
    *   sqlrrcom_dps                                               *
    *   sqlrrcom                                                   *
    *   sqlrr_commit                                               *
    *   sqljs_ddm_rdbcmm                                           *
    *   sqljsParseRdbAccessed                                      *
    *                                                              *
    * The stack trace might vary. But, due to the heavy latch      *
    * contention on headLsnSem, the performance will be impacted   *
    * significantly.                                               *
    *                                                              *
    * The fix for this APAR will reduce the latch contention on    *
    * SQLO_LT_SQLP_DBCB__headLsnSem.                               *
    *                                                              *
    *                                                              *
    *                                                              *
    *                                                              *
    *                                                              *
    * To reduce the chance of hitting this problem, following      *
    * methods can help increase the frequency of flushing dirty    *
    * pages.                                                       *
    * - set db cfg parameter SOFTMAX to a small value less than    *
    * 100, eg. SOFTMAX=25.                                         *
    * - specify separated buffer pool for different temp           *
    * tablespaces.                                                 *
    ****************************************************************
    * RECOMMENDATION:                                              *
    * Update to db2 version 9.7 fixpack 6 or later fixpacks.       *
    ****************************************************************
    

Problem conclusion

  • The enhancement fix is first provided in db2 version 9.7 fixpack
    6.
    

Temporary fix

  • To reduce the chance of hitting this problem, following methods
    can help increase the frequency of flushing dirty pages.
    - set db cfg parameter SOFTMAX to a small value less than 100,
    eg. SOFTMAX=25.
    - specify separated buffer pool for different temp tablespaces.
    

Comments

APAR Information

  • APAR number

    IC80305

  • Reported component name

    DB2 FOR LUW

  • Reported component ID

    DB2FORLUW

  • Reported release

    970

  • Status

    CLOSED PER

  • PE

    NoPE

  • HIPER

    NoHIPER

  • Special Attention

    NoSpecatt

  • Submitted date

    2011-12-08

  • Closed date

    2012-06-04

  • Last modified date

    2012-06-04

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

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

    IC85237

Fix information

  • Fixed component name

    DB2 FOR LUW

  • Fixed component ID

    DB2FORLUW

Applicable component levels

  • R970 PSY

       UP

  • RA10 PSY

       UP

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Document Information

Modified date:
04 June 2012