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PK75626: ENABLE AUTOMATIC WLM BUFFER POOL MANAGEMENT

A fix is available

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APAR status

  • Closed as unreproducible in next release.

Error description

  • Automatic bufferpool management using WLM support does not work.
    

Local fix

Problem summary

  • ****************************************************************
    * USERS AFFECTED: All users of DB2 for z/OS.                   *
    ****************************************************************
    * PROBLEM DESCRIPTION: Delivery of DB2 9 for z/OS WLM Buffer   *
    *                      Pool Management and enabling of DB2     *
    *                      WLM Delay Monitoring Support            *
    ****************************************************************
    * RECOMMENDATION:                                              *
    ****************************************************************
    When DB2 9 for z/OS was made generally available, its
    announced support for z/OS 1.8 WLM Buffer Pool Management
    capability was disabled.  The DB2 WLM delay monitoring
    capability was also disabled prior to general availability
    of DB2 9 for z/OS by APAR PK34179.
    

Problem conclusion

Temporary fix

Comments

  • The DB2 9 for z/OS support for z/OS V1R8 WLM buffer pool
    management capability is now available for use.  This
    capability is activated for a buffer pool when a buffer pool
    is defined or altered by the ALTER BUFFERPOOL command with
    the AUTOSIZE option set to YES.  Each time DB2 processes
    an ALTER BUFFERPOOL command against a buffer pool that
    already has the AUTOSIZE(YES) attribute or is being altered
    to have the AUTOSIZE(YES) attribute, DB2 will register the
    buffer pool with WLM.  In the registraton of the buffer pool
    with WLM, DB2 will use the current defined size of the
    buffer pool or the size specified with the VPSIZE option
    of the command as the buffer pool's initial size and DB2
    will use this initial size to calculate a maximum size
    and a minimum size for the buffer pool which are also told
    to WLM during the registration request.  The maximum size
    of a buffer pool will be calculated to be 1.25 times the
    initial size and the minimum size of a buffer pool will be
    calculated to be 0.75 times the initial size.
    As a CICS, IMS, or distributed task executes, DB2 will report
    to WLM that a delay has occurred to the task due to a DB2
    buffer pool I/O wait.  A buffer pool I/O wait occurs when a
    task has to wait for a buffer pool page to be read into
    memory.  This is called a synchronous database I/O wait.
    When WLM has to decide on a policy adjustment, it looks at
    the various service classes that have been used to manage
    work.  If any of those service classes have not met their
    performance goals (i.e. the performance indicator (PI) of
    the service class is greater than 1), WLM then analyzes
    the various delays that have been tracked against the
    service class, and if a large portion of the delays had
    been due to buffer pool I/O waits for a particular buffer
    pool, WLM may trigger an alter to the size of the buffer
    pool.  When this occurs, a DB2 message, DSNB555I, will be
    issued stating that a buffer pool is being changed from
    its current size to a new size.  The setting of the buffer
    pool to the indicated new size is processed by DB2 as if
    an ALTER BUFFERPOOL command was issued but DB2 does not
    reregister the buffer pool with WLM.  Thus, the buffer
    pool's new size will become the buffer pool's initial size
    when the buffer pool is reallocated after previously being
    deleted.  When DB2 deletes a buffer pool because it is no
    longer needed, it will deregister the buffer pool from WLM.
    During buffer pool reallocation, DB2 will reregister the
    buffer pool with WLM but the maximum and minimum sizes will
    be based on the new size of the buffer pool.
    WLM can issue a change which either increases or decreases
    the size of a buffer pool.  A buffer pool could be decreased
    in size if WLM observes that available real storage is being
    severely over-committed.  The z/OS WLM APAR, OA18461, should
    also be applied so that WLM will request that a DB2 buffer
    pool be altered.
    This APAR also restores general DB2 WLM delay monitoring
    support.
    
    **Urgent, Please Read**
    Please apply z/OS WLM APAR OA32631 to avoid Spin Loops with
    AUTOSIZE(YES)04E RC00E20003 DSNSVBK +05EA . EXCESS REPT BLOCKS
    

APAR Information

  • APAR number

    PK75626

  • Reported component name

    DB2 OS/390 & Z/

  • Reported component ID

    5740XYR00

  • Reported release

    910

  • Status

    CLOSED UR1

  • PE

    NoPE

  • HIPER

    NoHIPER

  • Special Attention

    YesSpecatt / New Function

  • Submitted date

    2008-11-13

  • Closed date

    2009-12-26

  • Last modified date

    2010-11-05

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

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

    UK53198

Modules/Macros

  • DSNB5WRA DSNDACOM DSNDDBPB DSNDSSCA DSNLAGNT
    DSNLCRTD DSNLCRTR DSNLIRTR DSNLTACT DSNLTZCH DSNTSTRT DSNVAI
    DSNVDBPB DSNVDBPM DSNVRMIM DSNVSDC0 DSNVSR   DSNVSRR  DSNVSRRX
    DSNVSRT  DSNVSRX  DSNXECPD DSNXERD  DSNYASCP DSN3CT30 DSN3CT80
    

Fix information

  • Fixed component name

    DB2 OS/390 & Z/

  • Fixed component ID

    5740XYR00

Applicable component levels

  • R910 PSY UK53198

       UP10/01/13 P F001

Fix is available

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Document Information

Modified date:
05 November 2010