RE: Q about Oracle Optimizer

From: Jon Walthour <jonw_at_fuse.net>
Date: Thu, 16 Aug 2001 04:04:35 -0700
Message-ID: <F001.0036CB1F.20010816035053@fatcity.com>

Volker:

If optimizer_mode = 'choose', then the optimizer chooses between cost-based optimization and rule-based optimization based on whether or not statistics are present. In your case, since they aren't it's using rule-based.

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

Volker
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: Jon Walthour
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