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PI31597: THE USE OF HIGH PERFORMANCE DBATS CAN RESULT IN UNEXPECTED LOCK TIMEOUTS. 15/05/12 PTF PECHANGE

A fix is available

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APAR status

  • Closed as program error.

Error description

  • DB2DDF DB2HIGHPERFDBAT defect pi31597 dpi31597
    If High Performance DBATs are being used, it is possible that
    locks acquired with duration allocation will not be released
    when the requester disconnects. A new connection may be assigned
    to this DBAT. This new connection, which can be from an
    application unrelated to the first use of the High Performance
    DBAT, may appear to inherit the locks from the earlier
    connection.
    

Local fix

Problem summary

  • ****************************************************************
    * USERS AFFECTED: All Distributed Data Facility (DDF) users    *
    *                 who are using, or plan to use,               *
    *                 High Performance DBAT support.  That is,     *
    *                 users which operate DDF with option          *
    *                 PKGREL(BNDOPT).                              *
    ****************************************************************
    * PROBLEM DESCRIPTION: Threads unexpectedly hold package and   *
    *                      table space intent locks.               *
    ****************************************************************
    * RECOMMENDATION:                                              *
    ****************************************************************
    DB2 10 for z/OS introduced a new DDF server thread processing
    mode called High Performance DBATs.  With APAR PI20352, DB2
    was changed to address situations where the activation of High
    Performance DBATs could lead to an increase in the CPU consumed
    to process distributed client requests.  The change enabled the
    pooling of high performance DBATs when the requesting client
    connection (using the DBAT) was terminated.
    When a High Performance DBAT is allowed to be pooled, as a
    result of the PI20352 change, any client connection could
    potentially be serviced by this DBAT - even a client
    connection that was not enabled to utilize a High
    Performance DBAT.  This results in application connections
    having (or inheriting) unexpected "package allocation" and/or
    "table space intent" locks from other unrelated applications.
    

Problem conclusion

  • DB2 has been changed to restore the prior (to APAR PI20352)
    PKGREL(BNDOPT) behavior.  But in order to accommodate client
    environments where any connection can utilize High Performance
    DBATs, DB2 has also been changed to support a new BNDPOOL
    High Performance DBAT processing option value via the
    -MODIFY DDF PKGREL(BNDPOOL) command.
    When DDF has been modified to run with a PKGREL value of
    BNDOPT, DDF will (again) terminate a High Performance DBAT
    when the client connection terminates.
    When DDF has been modified to run with a (new) PKGREL value of
    BNDPOOL, DDF will pool a high performance DBAT when the client
    connection terminates.
    Thus, for those customers who configure client environments
    with or without the ability to use High Performance DBATs, a
    PKGREL value of BNDOPT may be the preferred value.  For
    those customers who just configure DDF server resources to
    allow any client connection to use High Performance DBATs,
    a PKGREL value of BNDPOOL may be the preferred value.
    
    Documentation changes are required to describe the function
    provided by this APAR.
    
    Changes to the DB2 10 and DB2 11 Messages Manuals.
    ---------------------------------------------------------------
    
    The explanation text of messages DSNL004I and DSNL302I is
    changed:
    
    * The description of the BNDOPT value of the PKGREL DDF
      processing option is changed to have an additional paragraph
      as follows:
    
      When a connection which has used a high performance DBAT
      terminates, the high performance DBAT will also be
      deallocated.
    
    * A description of a new PKGREL DDF processing option value,
      BNDPOOL, is added as follows:
    
      BNDPOOL
    
      DDF processing for the BNDPOOL option value will be the
      same as the BNDOPT option value with the following
      exception:  when a connection which has used a high
      performance DBAT terminates, the high performance DBAT
      will be pooled.  The pooled DBAT can then be used by
      any other connection which presents a request to this
      DB2 subsystem.
    
    
    Changes to the DB2 10 and DB2 11 Command Reference manuals.
    ---------------------------------------------------------------
    
    The description of the PKGREL option of the MODIFY DDF command
    is replaced with the following:
    
    PKGREL
    
    Specifies whether DB2 honors the bind options of packages that
    are used for remote client processing. The PKGREL option also
    controls the disposition of high performance DBATs when a
    client connection which has used a high performance DBAT has
    terminated.
    
    BNDOPT
    The rules of the RELEASE bind option that was specified when
    the package was bound are applied to any package that is used
    for remote client processing.  The high performance DBAT used
    by a terminating client connection will be deallocated.
    BNDOPT is the default value of the MODIFY DDF PKGREL command.
    
    BNDPOOL
    The rules of the RELEASE bind option that was specified when
    the package was bound are applied to any package that is used
    for remote client processing.  The high performance DBAT used
    by terminating a client connection will be pooled.
    
    COMMIT
    The rules of the RELEASE(COMMIT) bind option are applied to
    any package that is used for remote client processing. COMMIT
    is the default value when the CMTSTAT subsystem parameter is
    set to ACTIVE. If the MODIFY DDF PKGREL command had never been
    issued, then COMMIT is the default value.  No high performance
    DBATs exist while the PKGREL option is set to COMMIT.
    
    The usages notes of the -MODIFY DDF command is changed as
    follows:
    
    When to use PKGREL options: You can specify that DDF uses the
    PKGREL(BNDOPT) or PKGREL(BNDPOOL) option during normal
    production operating hours.  For environments where client
    configurations control the use of packages which were bound
    with the RELEASE(DEALLOCATE) bind option, BNDOPT will be the
    preferred value of the PKGREL option.  For environments where
    any client is capable of using packages bound with the
    RELEASE(DEALLOCATE) bind option, BNDPOOL will be the preferred
    value of the PKGREL option.  Either option value offers
    improved performance by reducing the amount of CPU costs for
    allocating and deallocating packages. However, packages that
    run under the rules of the RELEASE(DEALLOCATE) bind option are
    likely to remain allocated and prevent maintenance activities
    such as objects modifications and bind operations.
    Consequently, you can use the PKGREL(COMMIT) option during
    routine and emergency maintenance periods.
    

Temporary fix

Comments

APAR Information

  • APAR number

    PI31597

  • Reported component name

    DB2 OS/390 & Z/

  • Reported component ID

    5740XYR00

  • Reported release

    A10

  • Status

    CLOSED PER

  • PE

    YesPE

  • HIPER

    NoHIPER

  • Special Attention

    YesSpecatt / New Function / Xsystem

  • Submitted date

    2014-12-15

  • Closed date

    2015-03-02

  • Last modified date

    2015-05-12

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

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

    UI25563 UI25564

Modules/Macros

  •    DSNGEFLC DSNGEPLC DSNLEDDA DSNLQCTL DSNLQDIS
    DSNLSSST DSNLTDDF DSNLTMDF DSNLXPRS DSN9SCNA
    

Publications Referenced
SC19405400SC19297200GC19406200GC19297900 

Fix information

  • Fixed component name

    DB2 OS/390 & Z/

  • Fixed component ID

    5740XYR00

Applicable component levels

  • RA10 PSY UI25563

       UP15/03/18 P F503

  • RB10 PSY UI25564

       UP15/03/18 P F503

Fix is available

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Document Information

Modified date:
06 May 2020