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Re: timed statistics

From: Don Granaman <granaman_at_home.com>
Date: Wed, 20 Jun 2001 08:17:02 -0700
Message-ID: <F001.003304DF.20010620083128@fatcity.com>

Timed statistics has very little performance impact - most of the work is already done internally anyway. It is very useful - for tkprof, wait statistics, and a few other things. I always set it and have for years - even on exceptionally hot OLTP systems. A guy I know from the Oracle Center of Expertise gave a talk to our local user group two weeks ago and mentioned that he had never seen any noticeable performance degradation due to setting it. If there is any significant performance impact, you have much bigger problems than timed statistics.

I have seen only one very specific bug related to setting it. That was just recently after upgrading an 8.1.7.0.0 OPS database on Sun Solaris to 8.1.7.1.0. Prior to the upgrade, no problem. After the upgrade, shutting down an instance while in parallel mode resulted in a long wait (several additional minutes, even with immediate) and an ORA-07445 error that generated a trace file and a cdump. The problem is that one of the OPS processes, bsp, would not shut down cleanly. This is one of the last things that happens during the instance shutdown. Since the database had already been dismounted, it probably isn't that serious. As far as I know, it only happens with PARALLEL_SERVER=TRUE in 8.1.7.1.0 (on Sun Solaris at least) and it did not happen in any prior release/patchlevel of 8i.

-Don Granaman
[certifiable OraSaurus]

> Hi
>
> Has anyone experienced any problems after setting timed_statistics to true
> on a prod database (at system level) ?
>
> Can anyone give me a guess as to the performance hit of doing this ?
>
> Running Oracle 8.1.6, there are fairly predictable periods of high,
medium,
> and low load so I can avoid collecting stats at peak periods if necessary.
>
> Cheers
> Greg
> --
> Please see the official ORACLE-L FAQ: http://www.orafaq.com
> --
> Author: Greg Solomon
> INET: greg.solomon_at_betfair.com
>
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-- 
Please see the official ORACLE-L FAQ: http://www.orafaq.com
-- 
Author: Don Granaman
  INET: granaman_at_home.com

Fat City Network Services    -- (858) 538-5051  FAX: (858) 538-5051
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Received on Wed Jun 20 2001 - 10:17:02 CDT

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