Terry Barnett wrote:
>I am having issues with execution plans changing even though the
>statistics on tables are kept static. Can anyone give me any information
>on the dynamic factors which are taken into account by the CBO when
>determining an execution plan and how one could detect that a plan may
>be about to change.
>
>Regards,
>Terry
>
>
>
Terry, if EVERYTHING is the same, then execution plans will not
change. If you, on the other hand, are running
9.2 database, have monitoring on for the tables involved, and have
OTPIMIZER_DYNAMIC_SAMPLING>0 (default is 1)
your optimizer will be smart enough to detect that your statisics is
stale (based on V$SEGMENT_STATISTICS) and gather
new statistics, based on 32 blocks (if ODS=1).
--
Mladen Gogala
Oracle DBA
Ext. 121
--
http://www.freelists.org/webpage/oracle-l
Received on Thu May 19 2005 - 16:25:52 CDT
