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IT07811: PARTIAL AGGREGATION OPERATOR CAN CAUSE MEMORY CORRUPTION LEADING TO DB2 INSTANCE ABEND

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You can track all active APARs for this component.

 

APAR status

  • Closed as program error.

Error description

  • Partial Aggregation operators (PED, PEA) may cause DB2 to abend
    due to a trap from invalid memory access and/or memory
    corruption.  This occurs due to writing past the end of an
    assigned memory range when either of the following occurs :
    - SORTHEAP has been dynamically reduced since the SQL statement
    was initially compiled, such as in an environment where STMM
    automatically tunes SORTHEAP
    - The sort reservation available to the operator is reduced due
    to throttling, i.e. the total sort reservation is approaching or
    exceeding SHEAPTHRES_SHR
    
    DB2 versions 10.1 and higher are vulnerable
    
    The db2diag.log will indicate that available memory is reduced
    as in the message below, though note that this alone is not
    enough to indicate the problem will definitely occur.  There
    must be an additional rare/specific shortage range resulting
    from the reduction which causes a logic error.
    
    XXXXXXXXXXXXXXXXXXXXXXXXXXXX        LEVEL: Warning
    EDUID   : XXXXX                EDUNAME: db2agent (XXXXX) 0
    FUNCTION: DB2 UDB, runtime interpreter, sqlriPEXInitHashTable,
    probe:3229
    MESSAGE : Partial Early Aggregation/Distinct running with
    reduced memory
    
    The trap symptoms can vary greatly due to the various
    side-effects resulting from memory corruption.  A common trap
    will have "Pea" in the function stack, such as:
    _intel_fast_memcpy
    sqlri_hsjnUnFormatPayload
    sqlriPeaPassAggValues
    sqlriPeaPassNonEmptyRec
    sqlriPeaEOF
    sqlripea
    

Local fix

  • Disable partial aggregation by the following :
      db2set DB2_REDUCED_OPTIMIZATION="NO_PEA,NO_PED"
      recycle the instance
    
    This is an internal registry variable setting to workaround this
    problem.  The setting should be removed upon upgrade to the Fix
    pack level containing this fix :
       db2set DB2_REDUCED_OPTIMIZATION=
       recycle the instance
    

Problem summary

  • ****************************************************************
    * USERS AFFECTED:                                              *
    * All DB2 systems are affected                                 *
    ****************************************************************
    * PROBLEM DESCRIPTION:                                         *
    * See Error Description                                        *
    ****************************************************************
    * RECOMMENDATION:                                              *
    * Upgrade to DB2 Version 10.1 Fix Pack 5                       *
    ****************************************************************
    

Problem conclusion

  • Problem first fixed in DB2 Version 10.1 Fix Pack 5
    

Temporary fix

  • see Local Fix
    

Comments

APAR Information

  • APAR number

    IT07811

  • Reported component name

    DB2 FOR LUW

  • Reported component ID

    DB2FORLUW

  • Reported release

    A10

  • Status

    CLOSED PER

  • PE

    NoPE

  • HIPER

    NoHIPER

  • Special Attention

    NoSpecatt

  • Submitted date

    2015-03-19

  • Closed date

    2015-07-30

  • Last modified date

    2015-07-30

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

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

    IT07899

Modules/Macros

  • sqri
    

Fix information

  • Fixed component name

    DB2 FOR LUW

  • Fixed component ID

    DB2FORLUW

Applicable component levels

  • RA10 PSN

       UP

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Document Information

Modified date:
30 July 2015