Re: db file scattered read
- From: Wolfgang Breitling <breitliw@xxxxxxxxxxxxx>
- To: oracle-l@xxxxxxxxxxxxx
- Date: Fri, 06 Aug 2004 20:23:25 -0600
I hope you're joking again.
Enabling "MONITORING" does not cause Oracle to automatically gather
statistics. As Justin pointed out, that doesn't happen until Oracle 10. In
9 you still need to schedule a gather_database|schema_stats "gather stale"
or "gather auto" job.
In theory, setting dynamic sampling to 4 should cause Oracle 9 to sample
statistics at parse time. Do you have any experience that it actually
works? I have tried on occasion to set dynamic sampling at the session
level, but unless the tables in the sql do not have statistics (in which
case you run the risk that the CBO is bypassed for the RBO if you have
optimizer_mode=choose => note to self to test if dynamic_sampling > 1
changes that "rule"), I have the strong impression that the CBO in many
cases does NOT sample statistics but simply uses the existing statistics.
Unless you jack up the level to much higher than 4, and even then not
always. I have to do more tests to be more certain.
At 07:43 PM 8/6/2004, you wrote:
>In 9i you sen set table to "MONITORING", and Oracle will collect statistics
>automatically. In 9i you can set dynamic sampling to 4 and Oracle will
>collect statistics during parse.
>
>--
>Mladen Gogala
>Oracle DBA
Regards
Wolfgang Breitling
Centrex Consulting Corporation
www.centrexcc.com
----------------------------------------------------------------
Please see the official ORACLE-L FAQ: http://www.orafaq.com
----------------------------------------------------------------
To unsubscribe send email to: oracle-l-request@xxxxxxxxxxxxx
put 'unsubscribe' in the subject line.
--
Archives are at //www.freelists.org/archives/oracle-l/
FAQ is at //www.freelists.org/help/fom-serve/cache/1.html
-----------------------------------------------------------------
Other related posts:
