RE: Should we stop analyzing?

From: Jesse, Rich <Rich.Jesse_at_qtiworld.com>
Date: Fri, 02 Jan 2004 09:54:31 -0800
Message-ID: <F001.005DB845.20040102095431@fatcity.com>

Jared, I think your conclusions must have assumptions:

The SQL was written "correctly".
The data structures wrer designed and layed out properly.

Here, we can AssUMe neither. :)

Food for thought...
Rich

Rich Jesse                           System/Database Administrator
rjesse_at_qtiworld.com                  Quad/Tech Inc, Sussex, WI USA

-----Original Message-----
Sent: Tuesday, December 30, 2003 4:29 PM To: Multiple recipients of list ORACLE-L

Mogens,

Quite a controversy you started here.

As always. ;)

I must admit this is the first time I've heard this come up.

As Jonathan stated, it does seem somewhat like rebuilding indexes.

But then again, if re-collecting statistics causes your database performance

to suddenly become very bad, it seems at first cut there are only two conclusions
you can come to.

CBO is broke if fresh statistics result in poor performance
statistics were collected at a time when temporary conditions created different statistics than what would normally appear. ie. at night when batch jobs are being run with lots of DML.

No. 2 seems the likely candidate, unless of course, it's both 1 and 2.

If just 2, then from a users perspective, it would seem most appropriate to have statistics collected during the day, when people are banging away on the OLTP stuff.

But then, might that play havoc with the batch jobs?

How about 2 sets of statistics. Import the OLTP stats in the morning for the users, and the BATCH stats at night for the batch jobs.

I'm not sure if I should laugh at that, or not.

Jared
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Author: Jesse, Rich
INET: Rich.Jesse_at_qtiworld.com

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