IC91989: QUERY WITH TABLESAMPLE SYSTEM() MIGHT HANG IN SMP MODE (INTRA_PARALLEL = YES)

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You can track all active APARs for this component.

APAR status

  • Closed as program error.

Error description

  • A query with TABLESAMPLE SYSTEM() might hang if it runs in
    parallel mode, i.e. INTRA_PARALLEL = YES.
    
    This issue was observed with ADMIN_MOVE_TABLE function which
    might use such queries starting with DB2 v10.1 Fixpack 1 (see
    also APAR IC84414).
    
    You might see a query like the following when executed with sub
    agents to hang:
    
    SELECT ...
    FROM <table> TABLESAMPLE SYSTEM() WITH UR;
    
    A stack trace against the coordinating agent might show
    "sqkfChannel::WaitRecvReady" function waiting to receive data
    from sub agents:
    
    ossDumpStackTraceInternal
    ossDumpStackTrace
    OSSTrapFile::dumpEx
    sqlo_trce
    sqloDumpDiagInfoHandler
    semtimedop
    sqloWaitEDUWaitPost
    sqkfChannel::WaitRecvReady
    sqkfChannel
    sqlkqrcv
    sqlktrcv
    sqlkt_unpack_tuple
    sqlktftc
    sqlritqa
    sqlriSectInvoke
    sqlrr_process_fetch_request
    sqlrr_open
    sqljs_ddm_opnqry
    sqljsParseRdbAccessed
    ...
    
    but in application snapshot there are no associated sub agents
    anymore.
    

Local fix

  • Do not use INTRA_PARALLEL, or turn parallelism off for the
    query, i.e.: SET CURRENT DEGREE = '1'
    

Problem summary

  • ****************************************************************
    * USERS AFFECTED:                                              *
    * ALL                                                          *
    ****************************************************************
    * PROBLEM DESCRIPTION:                                         *
    * See Error Description                                        *
    ****************************************************************
    * RECOMMENDATION:                                              *
    * Upgrade to DB2 Version 10.1 Fix Pack 3.                      *
    ****************************************************************
    

Problem conclusion

  • First fixed in DB2 Version 10.1 Fix Pack 3.
    

Temporary fix

Comments

APAR Information

  • APAR number

    IC91989

  • 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

    2013-04-30

  • Closed date

    2013-09-27

  • Last modified date

    2013-09-27

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

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

    IC95295

Fix information

  • Fixed component name

    DB2 FOR LUW

  • Fixed component ID

    DB2FORLUW

Applicable component levels

  • RA10 PSN

       UP



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Document information


More support for:

DB2 for Linux, UNIX and Windows

Software version:

10.1

Reference #:

IC91989

Modified date:

2013-09-27

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