PI96833: INCORRECT LOCK STATE REQUESTED BY UPDATE DELETE MERGE TRANSACTIONS ACCESSING UTS TABLE SPACE WITH A LOB COLUMN

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• Transactions performing UPDATE , DELETE, MERGE
  operations typically need to apply predicates to
  determine whether a row qualifies or not. When a lock
  is needed during this process, an UPDATE page/row (U-lock) is
  normally used. However, when the table is a Universal
  Table Space (UTS) with a LOB column it is possible that an IS
  ( Intent Shared )lock is used.
  This can lead to a deadlock or timeout when many concurrent
  threads need to access this page/row, as the lock is being
  upgraded to an X-lock in case the row is actually updated
  / deleted.
  

Local fix

• N/A
  

Problem summary

• ****************************************************************
  * USERS AFFECTED:                                              *
  * All Db2 12 for z/OS users of                                 *
  * Large OBjects (LOBS).                                        *
  ****************************************************************
  * PROBLEM DESCRIPTION:                                         *
  * Unexpected deadlock might be                                 *
  * experienced by applications executing                        *
  * UPDATE/DELETE/MERGE statements on                            *
  * tables in a UTS containing LOB                               *
  * columns.                                                     *
  ****************************************************************
  * RECOMMENDATION:                                              *
  * Apply corrective PTF when available                          *
  ****************************************************************
  Unexpected deadlock might be experienced by applications
  executing UPDATE/DELETE/MERGE statements on tables
  in a UTS containing LOB columns.
  
  The reason for the unexpected deadlocks is that Db2 fails
  to clean up a residual lock state.
  

Problem conclusion

• Db2 is corrected to use the correct lock state for
  UPDATE/DELETE/MERGE statements.
  

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:

  UI55561

Modules/Macros

• DSNICLOB
  

Fix information

• Fixed component name

  DB2 OS/390 & Z/

• Fixed component ID

  5740XYR00

Applicable component levels

• RC10 PSY UI55561

     UP18/05/12 P F805

Fix is available

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