PK55838: DBATS USING SEQUENCE OBJECTS DO NOT GO INACTIVE AFTER PK32436. THIS CAN RESULT IN ABEND04E, RC00D3003B 07/11/30 PTF PECHANGE

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• DB2DDF DDFL09 DB2INACTIVE defects pk55838 dpk55838
  A distributed thread using sequence objects will not go inactive
  after it commits if the fix for PK32436 is installed. This can
  result in the thread getting timed out for exceeding the idle
  thread timeout specification in zparm IDTHTOIN.
  00D3003B
  ***********************************************
  Additional symptoms and keywords:
    MSGDSNL027I DSNL027I 00D3003B RC00D3003B
      Idle Thread Time-out Timeout
    Missing reduced fewer IFCID 3 0003 IFCID3 IFCID0003
      accounting records
    SEQUENCE SEQUENCES PREVVAL PREVAL
      ACESQACT SeQuences ACTive
    SQLCODE -845 SQLCODE845 SQL845N SQL0845N
    DSN6FAC CMTSTAT INACTIVE
    DSNTIPR DDF THREADS INACTIVE
  

Local fix

Problem summary

• ****************************************************************
  * USERS AFFECTED: All Distributed Data Facility (DDF) users.   *
  *                 Specifically those that exploit the use      *
  *                 of SQL Sequences, and those where DB2 is     *
  *                 configured with DDF THREADS=INACTIVE         *
  *                 specified (DSN6FAC CMTSTAT INACTIVE) or      *
  *                 those with client systems (such as           *
  *                 DB2 UDB/LUW) that pool/re-use connections    *
  *                 among numerous client applications.          *
  ****************************************************************
  * PROBLEM DESCRIPTION: IFCID 3 accounting records are          *
  *                      not written and/or a high rate of       *
  *                      unexpected "Idle Thread Time-out"       *
  *                      (reason code 00D3003B) detections       *
  *                      may occur because a DDF server thread   *
  *                      is not allowed to become inactive       *
  *                      due to the use of SQL Sequences.        *
  *                      Client "connection concentrator"        *
  *                      environments may also be adversely      *
  *                      affected as a result of an inability    *
  *                      to pool connections on a transaction    *
  *                      (commit/rollback) boundary.             *
  ****************************************************************
  * RECOMMENDATION:                                              *
  ****************************************************************
  To correct remote client application incorrect output
  conditions related to the use of Sequences PREVVAL after a
  Commit or Rollback, and due to the complexity and risk
  associated with implementing a save and restore mechanism to
  maintain the Sequences environment across transaction
  boundaries, APAR PK32436 made a change to prevent DB2 z/OS
  threads and connections from being pooled when SQL Sequences
  are involved. That is, the solution corrected the Sequences
  incorrect output condition at the expense of preventing
  DB2 z/OS threads and connections from being pooled. This
  solution imposes too much adverse operational impact to
  application environments that use Sequences, especially since
  most of these environments are not dependent on PREVVAL values
  spanning transaction boundaries. Symptoms may include:
  . Increased number of concurrent Data Base Access Threads
    (DBATs) are required in order to service work because
    existing DBATs cannot be pooled to service the work.
  . Increased number of concurrent remote connections are required
    by remote client systems since existing connections cannot be
    pooled and re-used.
  . Increased occurrences of Idle Thread Time-out (00D3003B)
    detection conditions.
  Negative performance and throughput characteristics may also be
  observed as a result of the PK32436-induced inability to have a
  limited number of threads and connections that can be used to
  service a large number of remote applications. This may also
  lead to higher consumption of storage and network resources
  which may also impact performance.
  

Problem conclusion

• The ability to save and restore SQL Sequences environments is
  too complex and risky for an APAR. However, DDF thread and
  connection pooling is more desirable than the rare exposure to
  erroneous Sequences PREVVAL behavior. As a result, changes will
  be made to effectively reverse the PK32436-induced impact to
  DDF thread and connection pooling behavior. This means that the
  Sequences PREVVAL value will not be able to span transaction
  boundaries as far as remote applications are concerned. As a
  result, when a thread or connection is pooled, DB2 will ensure
  that the existing, if any, Sequences environment is destroyed
  in order to prevent an erroneous Sequences environment from
  being inherited by new users of the thread or connection.
  Hence, if a remote application attempts to resume their use of
  the Sequences PREVVAL value in a new transaction, a -845 SQLCODE
  may now be returned.
  The ability to save and restore the SQL Sequences environment,
  and hence allow pooling *and* the ability for Sequences PREVVAL
  references to be made across transaction boundaries, will be
  addressed in a future release of DB2. Until that time, in cases
  where applications desire the ability to reference PREVVAL
  across transaction boundaries, the DB2 z/OS SQL Reference
  manual will be changed to describe an application programming
  technique where a cursor can be defined WITH HOLD. The
  WITH HOLD nature of the cursor will prevent DDF thread and
  connection pooling and hence allow the desired PREVVAL behavior
  for remote applications.
  

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:

  UK31712 UK31713

Modules/Macros

• DSNDACE  DSNLQDIS DSNLQINA DSNLTCM1 DSNLTDSR
  DSNLTRB1 DSNTACT
  

Fix information

• Fixed component name

  DB2 OS/390 & Z/

• Fixed component ID

  5740XYR00

Applicable component levels

• R810 PSY UK31712

     UP07/12/14 P F712 

• R910 PSY UK31713

     UP07/12/14 P F712 

Fix is available

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