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IT21936: DB2 OPTIMIZER MIGHT PRODUCE SUB-OPTIMAL ACCESS PLAN FOR QUERY REFERENCING COLUMN ORGANIZED TABLE WITH PRIMARY KEY

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APAR status

  • Closed as program error.

Error description

  • If your query joins multiple column organized tables, and a
    primary key is defined on one or more of those tables, then the
    optimizer might incorrectly estimate the cost of the table
    access, possibly producing a sub-optimal access plan.
    
    If you encounter this error, you will either experience
    sub-optimal performance or receive a SQL0955 error.
    

Local fix

  • You can apply an optimization guideline to request the optimizer
    to choose the optimal join order.  You might also need to
    examine the statistics collected to determine if they are
    sufficient; for example column group statistics or a statistical
    view might be required to correct potential errors in the
    cardinality estimates in the optimizer's access plan.  Doing so
    can help protect against the optimizer choosing a sub-optimal
    access plan.
    

Problem summary

  • ****************************************************************
    * USERS AFFECTED:                                              *
    * ALL                                                          *
    ****************************************************************
    * PROBLEM DESCRIPTION:                                         *
    * See Error Description                                        *
    ****************************************************************
    * RECOMMENDATION:                                              *
    * Upgrade to Db2 11.1 Mod 3 Fix Pack 3 or higher               *
    ****************************************************************
    

Problem conclusion

  • First fixed in Db2 11.1 Mod 3 Fix Pack 3
    

Temporary fix

Comments

APAR Information

  • APAR number

    IT21936

  • Reported component name

    DB2 FOR LUW

  • Reported component ID

    DB2FORLUW

  • Reported release

    B10

  • Status

    CLOSED PER

  • PE

    NoPE

  • HIPER

    NoHIPER

  • Special Attention

    NoSpecatt / Xsystem

  • Submitted date

    2017-08-09

  • Closed date

    2018-03-19

  • Last modified date

    2018-03-19

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

    IV89728

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

Fix information

  • Fixed component name

    DB2 FOR LUW

  • Fixed component ID

    DB2FORLUW

Applicable component levels

  • RB10 PSN

       UP

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Document Information

Modified date:
19 March 2018