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

Obtain the fix for this APAR.

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 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.