RE: Alter table monitoring ... impact on performance??

That's the one I had in mind.

It was from Steve.

Jared

"Reardon, Bruce (CALBBAY)" <Bruce.Reardon_at_comalco.riotinto.com.au> Sent by: root_at_fatcity.com
 01/16/2003 03:59 PM
 Please respond to ORACLE-L  

        To:     Multiple recipients of list ORACLE-L <ORACLE-L_at_fatcity.com>
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        Subject:        RE: Alter table monitoring ... impact on performance??

>From Steve Adam's July 2000 newsletter (http://www.ixora.com.au/newsletter/2000_07.htm, line spacing below is mine):

"
Despite the potential for improved statistics gathering, many DBAs have not yet adopted modification monitoring.

One of the concerns that people have is that the monitoring might have a significant performance overhead.
In fact, this is not the case.

The modification counts are maintained in an efficient hash table is the SGA, and are updated without the protection of a latch (although the structure of the hash table itself is protected by the hash table modification latch). Even in heavy OLTP environments, the cost of maintaining the modification counts is likely to be less than 1% of additional CPU usage. However, because of the latch-free nature of the feature, the modification counts are not guaranteed to be accurate. Another source of potential inaccuracy is that if a transaction is rolled back, its changes to the modification counts are not rolled back as well. These inaccuracies have been allowed by Oracle to keep the performance overhead of this feature minimal. Therefore, you can use modification monitoring with confidence that it will not affect performance significantly, while giving you a very helpful indication of which tables may have stale statistics.
"

HTH,
Bruce Reardon

-----Original Message-----
Sent: Friday, 17 January 2003 10:26 AM

I've seen mention a of negligible performance hit for this.

It was from someone I trust, but I can't recall just who that was.

Jared

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