IBM Support

LO91353: BAD QUERY EXECUTION PLAN WHEN A FEW USERS HAVE VERY LARGE DATA SET.

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APAR status

  • Closed as program error.

Error description

  • Customer encountered a large increase in CPU usage on their DB2
    servers hosting the IBM Traveler database.  DB2 support was able
    to go on site and investigate in depth.  What was found is that
    the customer had 2 users with approximately 500,000 mail
    documents and unlimitted mail filters.  In this scenario the DB2
    Query optimizer picked an index execution plan that was very
    heavy on CPU.  Cleaning up these two users to less than 20,000
    documents each resolved the problem and the DB2 optimizer picked
    a more efficient Query execution plan.
    
    This APAR will be used to provide a schema or query update to
    prevent this from happening when a customer has some number of
    users with very large data sets.
    

Local fix

  • Limitting these large users to a 30 day mail filter will resolve
    as would simply deleting or archiving old mail.
    

Problem summary

  • IBM performance teams were able to reproduce with users who had
    large data sets.  In this case DB2 would choose a non-optimal
    query execution plan.  Though the issue may lie with DB2 itself,
    it was found that updating the index schema prevents this issue.
    

Problem conclusion

  • The IBM Traveler index schema was update to prevent this issue.
    

Temporary fix

Comments

APAR Information

  • APAR number

    LO91353

  • Reported component name

    LOTUS NOTES TRA

  • Reported component ID

    5724E6204

  • Reported release

    901

  • Status

    CLOSED PER

  • PE

    NoPE

  • HIPER

    NoHIPER

  • Special Attention

    NoSpecatt / Xsystem

  • Submitted date

    2017-01-19

  • Closed date

    2017-02-10

  • Last modified date

    2017-02-10

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

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

Fix information

  • Fixed component name

    LOTUS NOTES TRA

  • Fixed component ID

    5724E6204

Applicable component levels

  • R901 PSY

       UP



Document information

More support for: IBM Traveler

Software version: 9.0.1

Reference #: LO91353

Modified date: 10 February 2017


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