PM56725: DB2 V10 INCREASE IN DBM1 TCB TIME AND OPEN/CLOSE ACTIVITY

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• Increase in DBM1 TCB times and dataset open / close activity
  after migrating to DB2 v10 CM9.
  

Local fix

• N/A
  

Problem summary

• ****************************************************************
  * USERS AFFECTED: DB2 users.                                   *
  ****************************************************************
  * PROBLEM DESCRIPTION: Excessive dataset open/close activity,  *
  *                      resulting in increased CPU time for the *
  *                      DBM1 address space.                     *
  ****************************************************************
  * RECOMMENDATION:                                              *
  ****************************************************************
  The deferred close process (responsible for closing excess data
  sets when DSMAX has been exceeded) builds a large candidate list
  which it may continue using for a long period of time (several
  hours).  Since this list is ordered by last-referenced time at
  the time the list was built, and the closing of candidates does
  not check to see if the reference time has changed, the order
  of closing datasets becomes less and less an LRU process the
  longer the list remains active.  This may result in incorrectly
  closing datasets which are currently being frequently accessed,
  rather than others which are not currently being used.  This
  may be particularly noticable if the list is built while one
  type of workload is being run (e.g. overnight batch jobs) but
  is still being used while another type of workload is being
  run (e.g. daytime online transactions).
  

Problem conclusion

• The deferred close process has been modified to skip datasets
  on its candidate list which have been referenced since the time
  the list was built.
  

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:

  UK77298 UK77309

Modules/Macros

• DSNB1DRN
  

Fix information

• Fixed component name

  DB2 OS/390 & Z/

• Fixed component ID

  5740XYR00

Applicable component levels

• RA10 PSY UK77298

     UP12/04/12 P F204

• R910 PSY UK77309

     UP12/04/12 P F204

Fix is available

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