IC78403: DB2 OPTIMIZER CAN CHOOSE A SUB-OPTIMAL PLAN FOR A TABLE THAT HAS A HIGH ROWS-PER-PAGE NUMBER

DB2 Version 9.1 Fix Pack 11  for Linux, UNIX and Windows
DB2 Version 9.1 Fix Pack 12  for Linux, UNIX and Windows

APAR status

• Closed as program error.

Error description

• When a table has a high rows-per-page number, DB2 optimizer can
  be too conservative with the estimate and as a result,
  prefetching may not occur for a IXSCAN-FETCH operation on such a
  table, even when the index has a high cluster ratio. This can
  result in a sub-optimal query plan.
  

Local fix

Problem summary

• ****************************************************************
  * USERS AFFECTED:                                              *
  * All                                                          *
  ****************************************************************
  * PROBLEM DESCRIPTION:                                         *
  * See Problem Description above.                               *
  ****************************************************************
  * RECOMMENDATION:                                              *
  * Upgrade to DB2 Version 9.1 Fix Pack 11.                      *
  ****************************************************************
  

Problem conclusion

• First Fixed in Version 9.1 Fix Pack 11.
  

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:

  IC78430 IC78431

Fix information

• Fixed component name

  DB2 FOR LUW

• Fixed component ID

  DB2FORLUW

Applicable component levels

• R820 PSN

     UP

• R910 PSN

     UP

• R950 PSN

     UP

• R970 PSN

     UP

• R980 PSN

     UP