PI82191: REAL STORAGE USAGE STATISTICS CONTAINED IN IFCID225 IFCID0225

Obtain the fix for this APAR.

APAR status

• Closed as new function.

Error description

• REAL STORAGE usage statistics.                           (44080)
  

Local fix

• n/a
  

Problem summary

• ****************************************************************
  * USERS AFFECTED: All DB2 z/OS V11 users. Requires z/OS        *
  *                 APAR OA50366 be installed and IFCID0503      *
  *                 enabled before non-zero values are returned  *
  *                 for the new IFCID0225 record fields.         *
  *                                                              *
  *                 OA50366 may be installed before or after     *
  *                 PI82191.                                     *
  ****************************************************************
  * PROBLEM DESCRIPTION: IFCID225 Real Storage statistics record *
  *                      shows the total number of Real Frames   *
  *                      charged to DB2, but many of these       *
  *                      frames may have been discarded and are  *
  *                      available for steal.                    *
  ****************************************************************
  * RECOMMENDATION:                                              *
  ****************************************************************
  The IFCID0225 storage statistics record contains field values
  for the number of Real Storage pages charged to DB2 for 31 and
  64-bit virtual. These values are the current high water values
  and would only be the actual frames in use if the system were
  actively paging and stealing all of the discarded frames, or
  the frames have been stolen to replenish the frame available
  queues. Systems that have large amounts of REAL MAIN
  MEMORY and never page would likely always display the high
  water value. When DB2 ZPARM RealStorage_Management is ON
  or AUTO, contracted pages or pages freed during thread
  termination, are DISCARDDATA KEEPREAL(YES) and remain backed
  and charged against DB2 until or unless they are stolen.
  

Problem conclusion

Temporary fix

Comments

• The IFCID0225 record will now contain a new bit flag,
  QW0225DPGS, indicating this record contains return values for
  the following new fields:
  - QW0225ShrStkstg_dpage
  - QW0225PriStg_dpage
  - QW0225ShrStg_dpage
  - QW0225ComStg_dpage
  
  These fields will be zero in all records if QW0225DPGS is OFF,
  or if macro call result return count is zero, or if OA50366 is
  not applied. The IARV64 COUNTPAGES option, which contains the
  new DISCARDPAGES(YES) keyword, will be issued only once each
  day at approximately midnight local time, if new IFCID0503 is
  active. At the time this function is performed, an increase in
  DB2 MSTR TCB time will be observed.  This increase may be many
  times the normal observed and is dependent on the amount of
  64-bit storage in-use by this member.  The collection occurs
  only once per day due to the cost of the serialization and
  instructions to return these values for each non-bufferpool
  object.  If RealStorage_management = OFF, or IFCID0503 is OFF,
  this request will not be issued since there would be no
  discarded frames or user does not want the data.  The above new
  fields represent the count of DISCARDED frames which have not
  been stolen or re-referenced since the DISCARD was performed.
  The actual Real Frames in use at this interval, may be
  calculated by the following where xxx = any one of the four
  different new count fields above:
  
  QW0225xxxStg_Real + QW0225xxxStg_Aux - QW0225xxxStg_dpage
  

APAR Information

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

  PI78979

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

  UI49142

Modules/Macros

• DSNDQWHS DSNDQW03 DSNLTMSC DSNTXSTB DSNVMON
  DSNWDFSM DSNWVINT DSNWVZXT DSNYASCP
  

Fix information

• Fixed component name

  DB2 OS/390 & Z/

• Fixed component ID

  5740XYR00

Applicable component levels

• RB10 PSY UI49142

     UP17/08/12 P F708

Fix is available

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