PM70046: SET ZPARM/PROFILE OPTIOWGT SETTING ENABLED FOR ENABLE OR DISABLE INPUT TO ALLEVIATE PERFORMANCE ISSUES

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• Subsystem parameter OPTIOWGT could be set to DISABLE especially
  after migration from V8. This can cause performance degradation.
  

Local fix

Problem summary

• ****************************************************************
  * USERS AFFECTED: Users of DB2 for z/OS using the              *
  *                 subsystem parameter (ZPARM) OPTIOWGT         *
  *                 and/or using OPTIOWGT in the                 *
  *                 DSN_PROFILE_ATTRIBUTES table.                *
  ****************************************************************
  * PROBLEM DESCRIPTION: THE PROBLEM THIS FIX ADDRESSES HAS THE  *
  *                      FOLLOWING REPORTED SYMPTOMS:            *
  *                                                              *
  *                         Performance regression after         *
  *                         migration to V10 when                *
  *                         subsystem parameter OPTIOWGT         *
  *                         is set to DISABLE                    *
  *                                                              *
  *                      PROBLEM SCENARIO:                       *
  *                                                              *
  *                      The reported performance issue occurred *
  *                      after several users migrated to V10     *
  *                      from V8 of DB2. The subsystem parameter *
  *                      OPTIOWGT was left disabled causing      *
  *                      performance regression. Since the       *
  *                      documentation has this parameter as     *
  *                      deprecated, it was thought that it      *
  *                      no longer was used or effective.        *
  ****************************************************************
  * RECOMMENDATION:                                              *
  ****************************************************************
  SUMMARY OF DB2 EVENTS:
  Even though the subsystem parameter OPTIOWGT was deprecated
  in the documentation for V10, the parameter still allows
  DISABLE/ENABLE to be set. Both values have effect on the I/O
  weighting used in the calculation of the best access path.
  By leaving it disabled, there will be a degradation of
  performance.
  

Problem conclusion

• DB2 has changed the subsystem parameter OPTIOWGT DISABLE value
  to equal ENABLE thereby preventing future performance problems.
  In addition and for consistency, the DSN_PROFILE_ATTRIBUTES
  table values for OPTIOWGT have also changed where DISABLE is
  the same as ENABLE.
  
  
  ADDITIONAL KEYWORDS:
  SQLPERFORMANCE OPTIOWGT SQLMIGRATION
  

Temporary fix

• *********
  * HIPER *
  *********
  

Comments

APAR Information

• APAR is sysrouted FROM one or more of the following:

• APAR is sysrouted TO one or more of the following:

  UK83168

Modules/Macros

• DSN@XAZP DSNTIDXA DSNTIDXB DSNTINST DSNTXAZP
  DSNT1RSP DSNWZIFA DSNXOMPS DSN6SPRM
  

Fix information

• Fixed component name

  DB2 OS/390 & Z/

• Fixed component ID

  5740XYR00

Applicable component levels

• RA10 PSY UK83168

     UP12/11/21 P F211

Fix is available

• Select the PTF appropriate for your component level. You will be required to sign in. Distribution on physical media is not available in all countries.