|
Problem IT06323
|
Status: Closed |
SUB-OPTIMAL QUERY PLAN IN DPF ENVIRONMENT WHEN DB2_WORKLOAD=SAP |
| product: |
DB2 FOR LUW / DB2FORLUW / A50 - DB2 |
| Problem description: |
The DB2 optimizer might produce a non-optimal access plan when
all of the conditions below are met
(1) in a DPF environment
(2) DB2_WORKLOAD=SAP registry variable is set
(3) queries fit the required criteria for the star schema join
(4) At least one of the join columns on the fact table has
highly skewed data distribution.
When this problem is encountered, the optimizer can
under-estimate the join cardinality and subsequently choose a
sub-optimal query plan. |
| Problem Summary: |
****************************************************************
* USERS AFFECTED: *
* DPF environment *
****************************************************************
* PROBLEM DESCRIPTION: *
* See Error Description *
****************************************************************
* RECOMMENDATION: *
* Upgrade to DB2 Version 10.5 Fix Pack 7 *
**************************************************************** |
| Local Fix: |
create a statistical view to cover the joins |
| Solution |
|
| Workaround |
not known / see Local fix |
| Timestamps |
Date - problem reported :
Date - problem closed :
Date - last modified :
| 05.01.2015
22.01.2016
22.01.2016 |
| Problem solved at the following versions (IBM BugInfos) |
|
| Problem solved according to the fixlist(s) of the following version(s) |
| 10.5.0.7
|
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