PM80804: USER LOB TABLE SPACE GROWTH WHEN SHARED BUFFER POOL WITH DSNDB01 SPT01

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• A user LOB table space was growing.
  This was due to a seemingly old value for read claim lrsn for
  the buffer pool. LOB space reuse is tracked at buffer pool level
  using oldest read claim LRSN. Any objects using a 32k buffer
  pool are considered when calculating the oldest reader Lrsn. The
  buffer pool was also shared by directory LOB table space
  dsndb01.spt01 and there was an old commit-LRSN for DSNDB01.SPT01
  which caused the problem.
  Additional keywords: commit lsn , read lsn , read only .
  

Local fix

Problem summary

• ****************************************************************
  * USERS AFFECTED: DB2 data sharing users.                      *
  ****************************************************************
  * PROBLEM DESCRIPTION: Table space growth due to old read-lsn  *
  *                      value.                                  *
  ****************************************************************
  * RECOMMENDATION:                                              *
  ****************************************************************
  Any table space with a LOB column will register its commit-lsn
  as a read-lsn.  However, the commit-lsn value can be very old
  if the object has been read-only for a long time.  This old
  read-lsn gets propagated to the buffer pool level in data
  sharing, and can prevent space reuse for other objects sharing
  the same buffer pool.
  

Problem conclusion

• The code which registers a commit-lsn as a read-lsn has been
  modified to use the current end-of-log lrsn if the object is
  currently read-only, rather than its local commit-lsn value.
  Additionally, the local commit-lsn tracking will be improved
  to allow for advancement when another member gives up its
  update interest.
  

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:

  UK92094

Modules/Macros

•    DSNB1CLM DSNB1PPP
  

Fix information

• Fixed component name

  DB2 OS/390 & Z/

• Fixed component ID

  5740XYR00

Applicable component levels

• RA10 PSY UK92094

     UP13/03/16 P F303

Fix is available

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