IBM Support

IT17488: SELECT AGAINST MDC TABLE WITH A RANGE PREDICATE IN SMP MIGHT RETURN A WRONG RESULT

Subscribe

You can track all active APARs for this component.

 

APAR status

  • Closed as program error.

Error description

  • In a rare timing scenario SQL doing a range table scan on a MDC
    table in SMP mode only could loose rows from the result set.
    
    There are optimizations in DB2 to determine the best next range
    for each subagent to scan based on the usage of the system.
    However, the calculation in the optimization does not ensure
    each scan range is within the MDC block boundary and end up with
    a range covering more than a single block.  On the other hand,
    block predicate evaluation on a MDC table scan is done only once
    per range since it does not expect the scan range to cross a
    block boundary, it can incorrectly skip pages that would have
    been qualified for the scan predicate.  And this is timing
    related.
    

Local fix

  • Disable SMP mode.
    Or don't specify a range predicate on the MDC columns.
    

Problem summary

  • ****************************************************************
    * USERS AFFECTED:                                              *
    * ALL                                                          *
    ****************************************************************
    * PROBLEM DESCRIPTION:                                         *
    * See Error Description                                        *
    ****************************************************************
    * RECOMMENDATION:                                              *
    * Upgrade to DB2 10.1 Fix Pack 6                               *
    ****************************************************************
    

Problem conclusion

  • First fixed in DB2 10.1 Fix Pack 6
    

Temporary fix

Comments

APAR Information

  • APAR number

    IT17488

  • Reported component name

    DB2 FOR LUW

  • Reported component ID

    DB2FORLUW

  • Reported release

    A10

  • Status

    CLOSED PER

  • PE

    NoPE

  • HIPER

    YesHIPER

  • Special Attention

    NoSpecatt / Xsystem

  • Submitted date

    2016-10-13

  • Closed date

    2017-03-02

  • Last modified date

    2017-03-02

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

    IT17395

  • 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

  • RA10 PSN UP

       FIX

[{"Business Unit":{"code":"BU058","label":"IBM Infrastructure w\/TPS"},"Product":{"code":"SSEPGG","label":"Db2 for Linux, UNIX and Windows"},"Component":"","ARM Category":[],"Platform":[{"code":"PF025","label":"Platform Independent"}],"Version":"10.1","Edition":"","Line of Business":{"code":"LOB10","label":"Data and AI"}}]

Document Information

Modified date:
02 March 2017