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IC80673: WRONG PREFETCH SIZE CALCULATION FOR AUTOMATIC STORAGE

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You can track all active APARs for this component.

APAR status

  • Closed as program error.

Error description

  • In case you use PREFETCHSIZE AUTOMATIC with AUTOMATIC STORAGE,
    there could be a miscalculation of the PREFETCH SIZE used.
    The intention of this APAR is to fix the the prefetch size
    calculation.
    However, there is a more subtle and complex issue here.  In our
    design, each table has a packed descriptor and the packed
    descriptor contains a bunch of information including the
    tablespace's prefetch size.  When the tablespace's prefetch size
    changes, we need to update the packed descriptors of ALL the
    tables and indexes within this tablespace.  This is a complex
    issue because the packed descriptors are stored in the system
    catalog.  This is how it's done in the ALTER TABLESPACE
    PREFETCHSIZE codepath.  However, the automatic storage codepath
    does not have the infrastructure to do all these. Fixing this is
    too risky to be done in an APAR fix. There is a simple
    workaround available:
    
    1. ALTER TABLESPACE PREFETCHSIZE <some number>
    2. ALTER TABLESPACE PREFETCHSIZE AUTOMATIC "
    

Local fix

  • 1. ALTER TABLESPACE PREFETCHSIZE <some number>
    2. ALTER TABLESPACE PREFETCHSIZE AUTOMATIC "
    
    NOTE: Workaround is good till new stripe set is not created.
    Once containers get filled and new stripe set needs to be
    created, then prefetch size will be miscalculated again.
    

Problem summary

  • ****************************************************************
    * USERS AFFECTED:                                              *
    * All                                                          *
    ****************************************************************
    * PROBLEM DESCRIPTION:                                         *
    * See Error Description                                        *
    ****************************************************************
    * RECOMMENDATION:                                              *
    * Upgrade to DB2 Version 9.7 Fix Pack 6.                       *
    ****************************************************************
    

Problem conclusion

  • First fixed in DB2 Version 9.7 Fix Pack 6.
    

Temporary fix

Comments

APAR Information

  • APAR number

    IC80673

  • Reported component name

    DB2 FOR LUW

  • Reported component ID

    DB2FORLUW

  • Reported release

    970

  • Status

    CLOSED PER

  • PE

    NoPE

  • HIPER

    NoHIPER

  • Special Attention

    NoSpecatt

  • Submitted date

    2012-01-05

  • Closed date

    2012-06-06

  • Last modified date

    2012-06-22

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

    IC80671

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

    IC84583

Fix information

  • Fixed component name

    DB2 FOR LUW

  • Fixed component ID

    DB2FORLUW

Applicable component levels

  • R970 PSN

       UP



Document information

More support for: DB2 for Linux, UNIX and Windows

Software version: 9.7

Reference #: IC80673

Modified date: 22 June 2012