LO91353: BAD QUERY EXECUTION PLAN WHEN A FEW USERS HAVE VERY LARGE DATA SET.
Direct links to fixes
Closed as program error.
Customer encountered a large increase in CPU usage on their DB2 servers hosting the IBM Traveler database. DB2 support was able to go on site and investigate in depth. What was found is that the customer had 2 users with approximately 500,000 mail documents and unlimitted mail filters. In this scenario the DB2 Query optimizer picked an index execution plan that was very heavy on CPU. Cleaning up these two users to less than 20,000 documents each resolved the problem and the DB2 optimizer picked a more efficient Query execution plan. This APAR will be used to provide a schema or query update to prevent this from happening when a customer has some number of users with very large data sets.
Limitting these large users to a 30 day mail filter will resolve as would simply deleting or archiving old mail.
IBM performance teams were able to reproduce with users who had large data sets. In this case DB2 would choose a non-optimal query execution plan. Though the issue may lie with DB2 itself, it was found that updating the index schema prevents this issue.
The IBM Traveler index schema was update to prevent this issue.
This fix is included in IBM Traveler 22.214.171.124 and later releases. For the latest IBM Traveler maintenance release see this technote: http://www.ibm.com/support/docview.wss?uid=swg24019529
Reported component name
LOTUS NOTES TRA
Reported component ID
NoSpecatt / Xsystem
Last modified date
APAR is sysrouted FROM one or more of the following:
APAR is sysrouted TO one or more of the following:
Fixed component name
LOTUS NOTES TRA
Fixed component ID
Applicable component levels
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