Deletion of Damaging Statistics
This section describes how BRCONNECT deletes damaging statistics for the cost-based optimizer of the Oracle database.
Pool and cluster tables (for Oracle 9i only) and tables that have the ACTIVE
flag set to N
in the DBSTATC
control table should not normally have statistics, since such statistics can negatively affect
database performance.
Activities
In the standard update statistics run, using brconnect -f stats -t all
, BRCONNECT checks whether such damaging statistics exist and deletes them if so.
You can delete such damaging statistics immediately with the following command:
brconnect -u / -c -f stats -t harmful -d
To delete statistics for other tables as well (only for test purposes), you can use the option -f allsel
:
brconnect -u / -c -f stats -t sdbah,sdbad -d -f allsel
Caution
Starting with Oracle 10g, all tables generally have optimizer statistics.