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DB2 - Problem description

Problem IC78431 Status: Closed

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

product:
DB2 FOR LUW / DB2FORLUW / 970 - DB2
Problem 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.
Problem Summary:
**************************************************************** 
* USERS AFFECTED:                                              * 
* All users.                                                   * 
**************************************************************** 
* PROBLEM DESCRIPTION:                                         * 
* See Error Description                                        * 
**************************************************************** 
* RECOMMENDATION:                                              * 
* Upgrade to version 9.7 Fix Pack 6 or later.                  * 
****************************************************************
Local Fix:
available fix packs:
DB2 Version 9.7 Fix Pack 6 for Linux, UNIX, and Windows
DB2 Version 9.7 Fix Pack 7 for Linux, UNIX, and Windows
DB2 Version 9.7 Fix Pack 8 for Linux, UNIX, and Windows
DB2 Version 9.7 Fix Pack 9 for Linux, UNIX, and Windows
DB2 Version 9.7 Fix Pack 9a for Linux, UNIX, and Windows
DB2 Version 9.7 Fix Pack 10 for Linux, UNIX, and Windows

Solution
Problem was first fixed in Version 9.7 Fix Pack 6. 
 
The fix is not enabled by default. To enable it, set the 
following registry: 
 
DB2_EXTENDED_OPTIMIZATION=PG_CR
Workaround
not known / see Local fix
BUG-Tracking
forerunner  : APAR is sysrouted TO one or more of the following: IC98878 
follow-up : 
Timestamps
Date  - problem reported    :
Date  - problem closed      :
Date  - last modified       :
31.08.2011
05.06.2012
28.01.2014
Problem solved at the following versions (IBM BugInfos)
9.7.FP6
Problem solved according to the fixlist(s) of the following version(s)
9.7.0.6 FixList
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