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IZ40474: SORT MAY CRASH DUE TO INTEGER DIVIDE BY ZERO FAULT IN RARE TIMING SCENARIO WHEN INTRA_PARALLEL ON.

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APAR status

  • Closed as program error.

Error description

  • When intra_parallel is enabled, a sort operation may be
    parallelized amongst many processes. Control information that is
    shared amongst the concurrent processes is protected by a
    latching protocol. However, one piece of control information is
    read without protection of the latch. Since this value may be
    modified at the same time by another process, reading this
    transient value may produce and invalid value. In this case the
    invalid 0 value was used as the denomentator in a division
    resulting in an crash. This would occur in very rare timing
    conditions.
    
    The stack of the crashing process would contain entries similar
    to:
    
    Signal #8 (SIGFPE) - (FPE_INTDIV:Integer divide by zero.)
     <StackTrace>
    sqlsEstimateNumberOfRowsForGrowth
    sqlsIncreaseSortBufferSize
    sqlsResizeSortBufferBeforeInsert
    sqlsinsr
    sqlrsinsr
    

Local fix

  • no workaround
    

Problem summary

  • When intra_parallel is enabled, a sort operation may be
    parallelized amongst many processes. Control information that is
    shared amongst the concurrent processes is protected by a
    latching protocol. However, one piece of control information is
    read without protection of the latch. Since this value may be
    modified at the same time by another process, reading this
    transient value may produce and invalid value. In this case the
    invalid 0 value was used as the denomentator in a division
    resulting in an crash. This would occur in very rare timing
    conditions.
    
    The stack of the crashing process would contain entries similar
    to:
    
    Signal #8 (SIGFPE) - (FPE_INTDIV:Integer divide by zero.)
     <StackTrace>
    sqlsEstimateNumberOfRowsForGrowth
    sqlsIncreaseSortBufferSize
    sqlsResizeSortBufferBeforeInsert
    sqlsinsr
    sqlrsinsr
    

Problem conclusion

  • First fixed in DB2 UDB Version v9.1, FixPak 8 and v9.5 FixPak
    FP4.
    

Temporary fix

Comments

APAR Information

  • APAR number

    IZ40474

  • Reported component name

    DB2 UDB ESE SOL

  • Reported component ID

    5765F4102

  • Reported release

    910

  • Status

    CLOSED PER

  • PE

    NoPE

  • HIPER

    NoHIPER

  • Special Attention

    NoSpecatt

  • Submitted date

    2008-12-19

  • Closed date

    2009-10-08

  • Last modified date

    2009-10-08

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

    IZ40473

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

Fix information

  • Fixed component name

    DB2 UDB ESE SOL

  • Fixed component ID

    5765F4102

Applicable component levels

  • R910 PSY

       UP

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Document Information

Modified date:
08 October 2009