RE: Question re System Statistics
- From: "Allen, Brandon" <Brandon.Allen@xxxxxxxxxxx>
- To: <wjwagman@xxxxxxxxxxx>, <oracle-l@xxxxxxxxxxxxx>
- Date: Fri, 15 Jun 2007 12:06:40 -0700
The point of system stats is to give the CBO the most accurate
information about the CPU and I/O performance of your system so I'd say
it's only necessary to gather new system stats whenever the performance
of your system changes so, e.g. if you make any hardware changes,
signficant code changes (e.g. add/remove/patch/upgrade an application),
or load changes (e.g. add/remove a significant amount of users or
transactions).
I like to gather my stats over several "typical" business days and then
average them and manually set my system stats to the average values
during a typical load. Of course if you have wide variations in load,
e.g. OLTP by day and batch/OLAP/DSS by night, then you might want to
switch between two different sets of stats (set a job to do this
automatically).
Aside from gathering new system stats after significant changes to the
system, I think a good approach is to periodically (maybe quarterly?)
gather your system stats in a staging table, and then compare those to
your system stats that are currently in effect and investigate any major
differences and then update your real system stats if warranted by the
results of your investigation.
HTH,
Brandon
-----Original Message-----
From: oracle-l-bounce@xxxxxxxxxxxxx
[mailto:oracle-l-bounce@xxxxxxxxxxxxx] On Behalf Of William Wagman
I would be interested in folks thoughts about how frequently system
statistics should be gathered
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