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DB2 - Problem description

Problem IC89609 Status: Closed

PERFORMANCE DEGRADATION WHEN SEQUENCE IS PRESENT IN THE SELECT LIST COLUMN

product:
DB2 FOR LUW / DB2FORLUW / 970 - DB2
Problem description:
Under rare scenarios, performance degradation might be noticed 
if the following conditions are true: 
 
1. There is a sequence present in the output column of select 
list 
2. There are two or more views in the subselect directly below 
the sequence 
 
eg. 
select SEQUENCE1.NEXTVAL, col1, col2 
from view1 v1 
where v1.col1 = 
   (select MAX(col1) 
   from view1 v1 
   where col2 = ?);
Problem Summary:
**************************************************************** 
* USERS AFFECTED:                                              * 
* All users on DB2 v97 FP8 and lower                           * 
**************************************************************** 
* PROBLEM DESCRIPTION:                                         * 
* See Error Description                                        * 
**************************************************************** 
* RECOMMENDATION:                                              * 
* Upgrade to DB2 V97 FP9                                       * 
****************************************************************
Local Fix:
Separate the sequence into a new subselect: 
 
select SEQUENCE1.NEXTVAL , col1, col2 
from 
(select * 
from view1 v1 
where v1.col1 = 
   (select MAX(col1) 
   from view1 v1 
   where col2 = ?));
available fix packs:
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 V97 FP9
Workaround
not known / see Local fix
BUG-Tracking
forerunner  : APAR is sysrouted TO one or more of the following: IC89670 IC91783 
follow-up : 
Timestamps
Date  - problem reported    :
Date  - problem closed      :
Date  - last modified       :
17.01.2013
17.12.2013
17.12.2013
Problem solved at the following versions (IBM BugInfos)
9.7.FP9
Problem solved according to the fixlist(s) of the following version(s)
9.7.0.9 FixList
9.7.0.9 FixList