PK75643: CHANGE DEFAULT VALUE OF OPTIOWGT FROM DISABLE TO ENABLE

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• The default value of subsystem parameter OPTIOWGT is being
  changed from DISABLE to ENABLE.                         (dk1162)
  
  DB2MIGV9/K
  

Local fix

Problem summary

• ****************************************************************
  * USERS AFFECTED: All DB2 Version 9.1 for z/OS users are       *
  *                 affected by this change.                     *
  ****************************************************************
  * PROBLEM DESCRIPTION: DB2 for z/OS Version 9.1 does not use   *
  *                      enhanced formula for CPU and I/O cost   *
  *                      balancing by default.                   *
  ****************************************************************
  * RECOMMENDATION:                                              *
  ****************************************************************
  APAR PK61277 (fixing PTF UK39140) added support in the DB2 V9
  optimizer for an improved formula for balancing the costs of
  input/output and CPU speeds.  This formula causes the optimizer
  to choose access paths that more accurately reflect recent
  improvements in System z processor speeds.
  .
  Use of the formula is controlled by a DB2 subsystem parameter
  named OPTIOWGT, which can be set to DISABLE or ENABLE.  Current-
  ly, the default for OPTIOWGT is DISABLE, meaning that optimizer
  uses the traditional cost balance formula.
  .
  As System z processor speeds continue to improve, the cost
  imbalance of the traditional formula is increasingly exposed.
  .
  

Problem conclusion

• In response, this APAR changes the default setting of OPTIOWGT
  from DISABLE to ENABLE so that DB2 access path selection can
  more accurately reflect faster CPU System z processor speed.
  .
  IBM recommends that all current DB2 Version 9.1 for z/OS cus-
  tomers who use OPTIOWGT=DISABLE now convert to OPTIOWGT=ENABLE.
  See the ++HOLD actions for instructions.
  

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:

  UK42565

Modules/Macros

• DSNTIDXA DSNTIJUZ DSNTINST DSN6SPRM
  

Fix information

• Fixed component name

  DB2 OS/390 & Z/

• Fixed component ID

  5740XYR00

Applicable component levels

• R910 PSY UK42565

     UP09/01/06 P F901

Fix is available

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