PM56725: DB2 V10 INCREASE IN DBM1 TCB TIME AND OPEN/CLOSE ACTIVITY

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APAR status

  • Closed as program error.

Error description

  • Increase in DBM1 TCB times and dataset open / close activity
    after migrating to DB2 v10 CM9.
    

Local fix

  • N/A
    

Problem summary

  • ****************************************************************
    * USERS AFFECTED: DB2 users.                                   *
    ****************************************************************
    * PROBLEM DESCRIPTION: Excessive dataset open/close activity,  *
    *                      resulting in increased CPU time for the *
    *                      DBM1 address space.                     *
    ****************************************************************
    * RECOMMENDATION:                                              *
    ****************************************************************
    The deferred close process (responsible for closing excess data
    sets when DSMAX has been exceeded) builds a large candidate list
    which it may continue using for a long period of time (several
    hours).  Since this list is ordered by last-referenced time at
    the time the list was built, and the closing of candidates does
    not check to see if the reference time has changed, the order
    of closing datasets becomes less and less an LRU process the
    longer the list remains active.  This may result in incorrectly
    closing datasets which are currently being frequently accessed,
    rather than others which are not currently being used.  This
    may be particularly noticable if the list is built while one
    type of workload is being run (e.g. overnight batch jobs) but
    is still being used while another type of workload is being
    run (e.g. daytime online transactions).
    

Problem conclusion

  • The deferred close process has been modified to skip datasets
    on its candidate list which have been referenced since the time
    the list was built.
    

Temporary fix

Comments

APAR Information

  • APAR number

    PM56725

  • Reported component name

    DB2 OS/390 & Z/

  • Reported component ID

    5740XYR00

  • Reported release

    A10

  • Status

    CLOSED PER

  • PE

    NoPE

  • HIPER

    NoHIPER

  • Special Attention

    NoSpecatt

  • Submitted date

    2012-01-25

  • Closed date

    2012-03-27

  • Last modified date

    2012-05-02

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

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

    UK77298 UK77309

Modules/Macros

  •    DSNB1DRN
    

Fix information

  • Fixed component name

    DB2 OS/390 & Z/

  • Fixed component ID

    5740XYR00

Applicable component levels

  • RA10 PSY UK77298

       UP12/04/12 P F204

  • R910 PSY UK77309

       UP12/04/12 P F204

Fix is available

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Document information


More support for:

DB2 for z/OS

Software version:

A10

Reference #:

PM56725

Modified date:

2012-05-02

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