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IC77848: DB2 MAY ABEND WHILE OPTIMIZER IS FORCED TO CHOOSE REPLICATED MQT IN DPF

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APAR status

  • Closed as program error.

Error description

  • When a query is matched to a set of MQTs, optimizer will
    determine which MQT to use in the access plan based on costing.
    User can override the costing decision and force optimizer to
    choose replicated MQT via registry control flag
    "FORCE_REPLICATED_MQT_MERGE". Under that setting, query
    compilation may crash with call StackTrace having pattern:
    
    sqlnq_qurqtbchild2pp
    ...
    sqlnr_exe
    
    
    To hit the problem, the following conditions should all be
    satisfied:
    
    o Registry variable "DB2_EXTENDED_OPTIMIZATION" setting
      includes flag "FORCE_REPLICATED_MQT_MERGE".
    
    o It is a DPF system.
    
    o In addition to REPLICATED MQT, there are non-REPLICATED MQT
      online as well.
    
    o The compiled query should contain "SELECT DISTINCT"
      operator, or "EXISTS" predicate, or "IN" predicate whose
      right operand is a subquery.
    

Local fix

  • Reset REPLICATED MQT enforcement.
    

Problem summary

  • ****************************************************************
    * USERS AFFECTED:                                              *
    * All                                                          *
    ****************************************************************
    * PROBLEM DESCRIPTION:                                         *
    * See Error Description above.                                 *
    ****************************************************************
    * RECOMMENDATION:                                              *
    * Upgrade to DB2 9.7 Fix Pack 5 or higher                      *
    ****************************************************************
    

Problem conclusion

  • First Fixed in DB2 Version 9.7 Fix Pack 5
    

Temporary fix

Comments

APAR Information

  • APAR number

    IC77848

  • 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

    2011-07-29

  • Closed date

    2012-03-12

  • Last modified date

    2012-03-12

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

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

    IC82501

Fix information

  • Fixed component name

    DB2 FOR LUW

  • Fixed component ID

    DB2FORLUW

Applicable component levels

  • R970 PSN

       UP

  • R970 PSY

       UP



Document information

More support for: DB2 for Linux, UNIX and Windows

Software version: 9.7

Reference #: IC77848

Modified date: 12 March 2012