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PH47163: ENHANCE DB2 REAL STORAGE MANAGEMENT WHEN USING REALSTORAGE_MANAGEMENT=AUTO

A fix is available

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APAR status

  • Closed as program error.

Error description

  • Enhance Db2 real storage management when using ZPARM
    REALSTORAGE_MANAGEMENT = AUTO (default).
    

Local fix

  • N/A
    

Problem summary

  • ****************************************************************
    * USERS AFFECTED:                                              *
    * All Db2 12 for z/OS users.                                   *
    ****************************************************************
    * PROBLEM DESCRIPTION:                                         *
    * Enhance Db2 REALSTORAGE_MANAGEMENT                           *
    * subsystem parameter                                          *
    ****************************************************************
    * RECOMMENDATION:                                              *
    * Apply corrective PTF when available                          *
    ****************************************************************
    There are Db2 users who saw significant increase in Db2 system
    service address space (SRB) CPU time.  This has been observed
    as one of the effects when processing excessive IARV64
    REQUEST(DISCARDDATA) requests.
    

Problem conclusion

  • The use of the Db2 REALSTORAGE_MANAGEMENT subsystem parameter
    was enhanced as follows:
    * introduce a new option AUTO1:
      This  new option will have the same behavior as AUTO prior to
      applying this PTF (PH47163)
    * modified behavior of option AUTO:
      Option AUTO will now check the available real storage on the
      LPAR.
      REALSTORAGE_MANAGEMENT=AUTO was specified but Db2 detected
      that the available real storage on the LPAR is more than the
      calculated threshold (REALAVAIL > MAXSPACE*1.2), Db2 switches
      behavior as if option OFF is specified, and does not discard
      unused real storage.  Otherwise, Db2 will behave as if AUTO1
      is specified
    * new message DSNS006I:
      New message, DSNS006I, will be issued when Db2 switches
      behavior
    The recommendation is to continue to use the current
    REALSTORAGE_MANAGEMENT setting, whether it be OFF, AUTO or ON.
    This PTF only changes the behavior for users whose current
    REALSTORAGE_MANAGEMENT setting is AUTO.
    After applying this PTF (PH47163), those users will see more
    dynamic use of discarddata processing.  This is expected to
    have positive effect on Db2 MSTR CPU time.
    Users executing with REALSTORAGE_MANAGEMENT=AUTO, who want to
    continue to have identical REALSTORAGE_MANAGEMENT behavior
    prior to applying this PTF (PH47163), must change the
    REALSTORAGE_MANAGEMENT subsystem parameter setting to AUTO1.
    DSNS006I
    csect DB2 WILL START TO BEHAVE AS
          REALSTORAGE_MANAGEMENT = value
    Explanation
    This message is issued when Db2 has detected one of the
    following conditions was satisfied and caused Db2 to change its
    behavior
    OFF   = REALSTORAGE_MANAGEMENT=AUTO was specified but Db2
            detected that available real storage on the LPAR is
            more than the calculated threshold
            (REALAVAIL > 1.2*MAXSPACE)
    AUTO1 = REALSTORAGE_MANAGEMENT=AUTO was specified but Db2 was
            behaving as if REALSTORAGE_MANAGEMENT=OFF. Now, the
            available real storage on the LPAR is no longer more
            than the calculated threshold (REALAVAIL <
            1.2*MAXSPACE), Db2 will behave as
            REALSTORAGE_MANAGEMENT=AUTO1
            OR
            REALSTORAGE_MANAGEMENT=AUTO but the available real
            storage on the LPAR is less than or equal to the
            calculated threshold (REALAVAIL < 1.2*MAXSPACE), Db2
            will behave as REALSTORAGE_MANAGEMENT=AUTO1
    Where
    REALAVAIL   The amount of real storage currently available on
                the LPAR
    MAXSPACE    z/OS setting that restricts the virtual storage
                available to the DUMPSRV address space to
                capture SVC dumps.
    
    For more information about this enhancement, see the
    description of this APAR in the Db2 for z/OS documentation:
    https://www.ibm.com/docs/en/SSEPEK_12.0.0/wnew/src/tpc/
    db2z_12_newfunctionapars.html
    
    Additional Keywords:
    DSNS006I REALSTORAGE_MANAGEMENT
    

Temporary fix

Comments

  • ×**** PE23/03/15 FIX IN ERROR. SEE APAR PH53275  FOR DESCRIPTION
    

APAR Information

  • APAR number

    PH47163

  • Reported component name

    DB2 OS/390 & Z/

  • Reported component ID

    5740XYR00

  • Reported release

    C10

  • Status

    CLOSED PER

  • PE

    NoPE

  • HIPER

    NoHIPER

  • Special Attention

    NoSpecatt / Xsystem

  • Submitted date

    2022-06-13

  • Closed date

    2023-01-25

  • Last modified date

    2023-05-02

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

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

    UI90276

Modules/Macros

  • DSN6SPRM DSNFSDIR DSNSVSFM DSNSVSVP DSNSCON2 DSNDQWPZ DSNWZIFC
    DSNFCDIR DSNVMON  DSNDSPRM DSNTIPE1
    

Fix information

  • Fixed component name

    DB2 OS/390 & Z/

  • Fixed component ID

    5740XYR00

Applicable component levels

  • RC10 PSY UI90276

       UP23/02/14 P F302

Fix is available

  • Select the PTF appropriate for your component level. You will be required to sign in. Distribution on physical media is not available in all countries.

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Document Information

Modified date:
03 May 2023