PH43985: POSSIBLE HANG WHEN LOCKING MULTIPLE TABLES

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• Possible hang when locking multiple tables in parallel (unload
  with LOCK YES option).
  Detected in debug mode with assert failure (Assertion failed:
  pthreadExpected == pthread in oenclaveMutexLock).
  The problem was detected through the code, to have a chance to
  reproduce it: run a hpu unload on a high number of tables with
  a high tablespace parallelism, with the LOCK YES option
  activated.
  A hang could happen if multiple threads are trying to lock a
  table at the same time.
  It might still be difficult to reproduce in that case, because
  it depends on the execution speed of the threads.
  Example of a job:
  LISTDEF LIST1 INCLUDE TABLESPACE DBTLS00.FRDCA2%
  UNLOAD TABLESPACE
  PARALLELISM(5,1,10)
  LOCK YES
  SELECT * FROM LIST(LIST1)
  

Local fix

Problem summary

• ****************************************************************
  * USERS AFFECTED: Users of Db2 High Performance Unload         *
  *                 for z/OS                                     *
  ****************************************************************
  * PROBLEM DESCRIPTION: An intermittent hanging situation can   *
  *                      occur during an unload that fulfills    *
  *                      the following conditions:               *
  *                      - the LOCK YES feature is requested     *
  *                      - at least two logical unloads are      *
  *                      requested both in:                      *
  *                        a) either native mode                 *
  *                        b) or SQL mode (b)                    *
  *                      - parallelism applying to the           *
  *                      processing mode of the set of two       *
  *                      unload is enabled, i.e.:                *
  *                        a) either TS parallelism as requested *
  *                           by PARALLELISM (,,n) with n        *
  *                           greater than 1                     *
  *                        b) or Db2 parallelism as requested by *
  *                           PARALLELISM (,n,) with n greater   *
  *                           than 1                             *
  *                                                              *
  *                      As this issue only occurs if very       *
  *                      specific timing conditions are          *
  *                      fulfilled this issue is very unlikely   *
  *                      and might not occur again if the        *
  *                      affected unload is run again.           *
  *                      It is more likely to occur if a very    *
  *                      big number of unloads are run with a    *
  *                      big parallelism degree such as in the   *
  *                      following example:                      *
  *                                                              *
  *                      LISTDEF LIST1 INCLUDE TABLESPACE MYDB.% *
  *                      UNLOAD TABLESPACE                       *
  *                      PARALLELISM(5,1,10)                     *
  *                      DB2 NO                                  *
  *                      LOCK YES                                *
  *                      SELECT * FROM LIST(LIST1)               *
  ****************************************************************
  * RECOMMENDATION: Apply the PTF                                *
  ****************************************************************
  Possible hang when locking multiple tables
  

Problem conclusion

• Code has been changed to fix this problem
  

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:

Modules/Macros

• INZUTILK
  

Fix information

• Fixed component name

  DB2 HI PERF UNL

• Fixed component ID

  5697F4400

Applicable component levels

• R510 PSY UI79968

     UP22/04/09 P F204

Fix is available

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