Latest versionsfixlist
11.1.0.7 FixList
10.5.0.9 FixList
10.1.0.6 FixList
9.8.0.5 FixList
9.7.0.11 FixList
9.5.0.10 FixList
9.1.0.12 FixList
Have problems? - contact us.
Register for free anmeldung-x26
Contact form kontakt-x26

DB2 - Problem description

Problem IC78742 Status: Closed

INACCURATE COLCARD STATISTICS UNDER RARE CONDITIONS WHICH CAN LEAD TO POOR
PERFORMANCE.

product:
DB2 FOR LUW / DB2FORLUW / 970 - DB2
Problem description:
Under rare conditions, the COLCARD statistics value of a column 
might be significantly inaccurate.  Inaccurate statistics might 
lead the query optimizer to determine a poor performing access 
plan. 
 
When a column is the leading column of an index, the index can 
be used to provide an accurate colcard.  When no such index is 
available, DB2 will estimate the colcard, and this is the 
situation where the problem may be observed. 
 
When the problem is observed, the inaccurate colcard determined 
will be 254 when TABLESAMPLE option is not used, and 1022 when 
the TABLESAMPLE option is used. 
 
If you suspect you are experiencing the problem, you can compare 
the colcard with the actual unique count for the column.  It is 
normal for the two to be different.  If the colcard estimate is 
highly inaccurate, and its value is either 254 or 1022, then you 
are possibly experiencing the problem.
Problem Summary:
**************************************************************** 
* USERS AFFECTED:                                              * 
* All users on DB2 v97 FP5 and earlier                         * 
**************************************************************** 
* PROBLEM DESCRIPTION:                                         * 
* See Error Description                                        * 
**************************************************************** 
* RECOMMENDATION:                                              * 
* Upgrade to DB2 9.7 FP6 or subsequent fix pack.               * 
****************************************************************
Local Fix:
As a workaround, if possible, create an index where the column 
is the leading column of the index, and then perform a table and 
index statistics collection using the AND INDEXES clause.
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
First Fixed in DB2 Version 9.7 Fix Pack 6
Workaround
not known / see Local fix
Timestamps
Date  - problem reported    :
Date  - problem closed      :
Date  - last modified       :
16.09.2011
22.06.2012
29.01.2013
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
This site uses cookies to make it easier for us to provide you with our services. By using our site you agree to the use of cookies.