PM75473: DDF THREADS INTERMITTENTLY TOOK MORE THAN 20 SECONDS TO FINISH. HIGH STORAGE MGR LATCH CONTENTION. ABENDS RC00E20003, RC00E20016

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• DB2DDF Defect pm75473 dpm75473
  DDF threads would slow down intermittently and took more than
  20 seconds to finish whereas usually it took less than one
  second to finish.  The incoming DDF threads were queued due to
  the slow down and then soon MAXDBAT was reached. Then the
  storage shortage abends 00E20003 or 00E20016 occurred.
  ***********************************************************
  Additional Symptoms and Keywords:
   Short On Storage SOS Performance PERF LCBLSTKP
   ABEND04E AB04E S004E 04E
    04E-00E20003 00E20003 RC00E20003
     DSNGEPLC DSNSVBK  DSNGEPLC.DSNSVBK +05EA
     DSNXEPM  DSNSVBK  DSNXEPM .DSNSVBK +05EA
     DSNXOTDA DSNSVBK  DSNXOTDA.DSNSVBK +05EA
    04E-00E20016 00E20016 RC00E20016
     DSNSLD1  DSNSVSTK DSNSLD1 .DSNSVSTK+0656
  

Local fix

Problem summary

• ****************************************************************
  * USERS AFFECTED: All Distributed Data Facility (DDF) users.   *
  ****************************************************************
  * PROBLEM DESCRIPTION: Intermittent performance problems may   *
  *                      be observed due to contention related   *
  *                      to DDF communication buffer storage     *
  *                      usage.                                  *
  *                      Unpredictable, storage related, abends  *
  *                      may also occur. Symptoms may include:   *
  *                      . ABND=04E-00E20003,                    *
  *                        LOC=DSNGEPLC.DSNSVBK +05EA            *
  *                      . ABND=04E-00E20003,                    *
  *                        LOC=DSNXEPM .DSNSVBK +05EA            *
  *                      . ABND=04E-00E20016,                    *
  *                        LOC=DSNSLD1 .DSNSVSTK+0656            *
  *                      . ABND=04E-00E20003,                    *
  *                        LOC=DSNXOTDA.DSNSVBK +05EA            *
  ****************************************************************
  * RECOMMENDATION:                                              *
  ****************************************************************
  To satisfy remote application SQL activity, distributed server
  threads may acquire vast amounts of 64-bit shared private
  (communication buffer) storage.  As storage utilization
  increases, delays of 20 seconds or more may occur when
  satisfying storage requests from a storage pool which has a
  limited number of extra blocks allowed by its definition.
  This may lead to application/transaction delays and/or storage
  related abends.
  

Problem conclusion

• DDF initialization has been changed to increase the number of
  extra blocks allowed to satisfy a get storage request to match
  the number of blocks that are actually requested at a time.
  This reduces the number of storage scans and expansions
  necessary to satisfy a "get storage" request thereby reducing
  latch contention.  This allows threads to get and release
  storage more quickly which minimizes abends due to storage
  shortage.  This leads to an improvement in overall DDF
  transaction response time.
  

Temporary fix

• *********
  * HIPER *
  *********
  

Comments

APAR Information

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

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

  UK91168 UK91169

Modules/Macros

• DSNLIINI
  

Fix information

• Fixed component name

  DB2 OS/390 & Z/

• Fixed component ID

  5740XYR00

Applicable component levels

• RA10 PSY UK91168

     UP13/02/09 P F302

• R910 PSY UK91169

     UP13/02/09 P F302

Fix is available

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