PK99362: EXCESSIVE HEAP STORAGE REQUESTS CAUSED PERFORMANCE DEGRADATION

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• Higher than expected overhead incurred in heap storage requests
  which resulted in performance degradation with the ODBC 64-bit
  driver.
  

Local fix

Problem summary

• ****************************************************************
  * USERS AFFECTED: All users of DB2 UDB for z/OS Version 9      *
  *                 ODBC/CLI in 64-bit mode.                     *
  ****************************************************************
  * PROBLEM DESCRIPTION: 1. Performance degradation due to       *
  *                         increasing number of storage         *
  *                         requests for 31-bit heap.            *
  *                      2. ABEND0C4 in CLI_qrsCallStoreProc     *
  *                         when application issues a CALL       *
  *                         statement that contains vendor       *
  *                         escape clause sequences.             *
  *                      3. ABEND0C4 in CLI_attiDSNHLI when      *
  *                         running with the z/OS CSVRENTSP252   *
  *                         DIAG trap.                           *
  ****************************************************************
  * RECOMMENDATION:                                              *
  ****************************************************************
  1. When interfacing with DB2 in 64-bit addressing mode,
     additional storage requests are made to acquire storage
     within the 31-bit address range.  These storage requests
     incur excessive latch overhead which may impact the
     overall performance of user applications.
  2. When processing a CALL statement that contains vendor escape
     clause sequences, storage was incorrectly acquired above
     the 31-bit address range while the pointer variable that
     is used to hold the returned address is only 32 bits long.
  3. During processing of SQL statements in 64-bit mode,
     the driver updates the contents of a string literal.
     This modification is intentional.  However, when the
     CSVRENTSP252 DIAG trap is enabled, only programs running
     in PSW key 0 are authorized to perform such modification.
     This causes ABEND0C4 in CLI_attiDSNHLI.
  

Problem conclusion

• 1. Code has been modified to provide the driver a more
     efficient means for acquiring and freeing 31-bit storage.
  2. Code has been modified to acquire storage within the
     31-bit address range.
  3. Code has been changed to avoid modifying any literal
     values in the load module.
  

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:

  UK52302

Modules/Macros

•    CLI      CLIATTI  CLISCN   CLIUNI   CLIUTL
  DSNAOCLI DSNAOC0T DSNAOC1V DSNAOC17 DSNAOG0T DSNAOG1V DSNAOG17
  DSNAOG29 DSNAOSDK
  

Fix information

• Fixed component name

  DB2 ODBC/JDBC/S

• Fixed component ID

  5740XYR02

Applicable component levels

• R917 PSY UK52302

     UP09/12/05 P F912

Fix is available

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