PM93375: PERFORMACE ELPASED TIME DEGRADATION AND INCREASED SYNCH I/O IN PARALLEL INDEX UPDATES.

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• Performace elpased time degradation and increased synch I/O in
  parallel index updates. Also, parallel index updates appear to
  be either reduced significantly or disabled in V11.    (d167833)
  Additional symptoms: 04E 00C20223 ABENDS0C4 S0C4 0C4
  

Local fix

• n/a
  

Problem summary

• ****************************************************************
  * USERS AFFECTED: DB2 V11 users.                               *
  ****************************************************************
  * PROBLEM DESCRIPTION: Performance degradation caused by       *
  *                      parallel index updates performing       *
  *                      synchronous reads.                      *
  *                                                              *
  *                      In data sharing, ABEND04E RC00C20223    *
  *                      in DSNB5ULK, or ABEND0C4 in DSNB5PCO.   *
  ****************************************************************
  * RECOMMENDATION:                                              *
  ****************************************************************
  Parallel index updates may perform excessive synchronous reads
  due to the setting of a "no prefetch" flag which is incorrectly
  applied to the processing of a conditional GetPage request.
  
  The DSNB5ULK and DSNB5PCO abends may occur when a castout engine
  is performing parallel I/Os, and the ROB which was designated
  for the wait for the first I/O is reused for another wait.
  

Problem conclusion

• The conditional GetPage logic has been modified to schedule the
  prefetch of the requested page when it is not already in the
  buffer pool, regardless of the setting of the "no prefetch"
  flag.
  
  The castout logic has been modified to allocate a separate ROB
  to be used for the wait for the first I/O, rather than using
  the CTBMROB for this purpose.
  

Temporary fix

Comments

APAR Information

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

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

  UK97639

Modules/Macros

• DSNB1GET DSNB5PCO
  

Fix information

• Fixed component name

  DB2 OS/390 & Z/

• Fixed component ID

  5740XYR00

Applicable component levels

• RB10 PSY UK97639

     UP13/10/03 P F310

Fix is available

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