RE: Q about Oracle Optimizer

From: Christopher Spence <cspence_at_FuelSpot.com>
Date: Thu, 16 Aug 2001 04:38:21 -0700
Message-ID: <F001.0036CC35.20010816045102@fatcity.com>

If the objects in a query have not been analyze, then rule mode is defaulted.

If there are objects in the database which are analyze, yet the tables you are using are not analyzed, rule mode will still be used.

If one table is analyzed, and it is joined with 5 others which are not analyzed, then cost base will be used.

There are a few parameters that need tweaking when you first go from rule to cost base.

"Do not criticize someone until you walked a mile in their shoes, that way when you criticize them, you are a mile a way and have their shoes."

Christopher R. Spence
Oracle DBA
Phone: (978) 322-5744
Fax: (707) 885-2275

Fuelspot
73 Princeton Street
North, Chelmsford 01863

-----Original Message-----

Sent: Thursday, August 16, 2001 4:46 AM
To: Multiple recipients of list ORACLE-L

Hi list,

a quick question about oracle optimizer.

a customer has database migrated from 7.3.4 to 8.1.6 on AIX. Data was transfered via full exp/imp. After migration the performance of the new database is very poor. I looked at the parameters and saw that no object is analyzed. So now me question:

What does oracle optimizer do, if there are no statistics on all objects. Optimizer level is choose.

Volker Schön
E-Mail: mailto:v.schoen_at_inplan.de
http://www.inplan.de

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Author: Schoen Volker
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Author: Christopher Spence
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