Optimizer change from 8i-9i

From: zhu chao <zhuchao_at_gmail.com>
Date: Mon, 9 May 2005 17:44:30 +0800
Message-ID: <962cf44b05050902444679d369@mail.gmail.com>

Hi, all,

We will recently migrate some important database server from 8i to 9i(9.2.0.5 with a bunch of fixes). As we have very high concurrency and load, we want to keep the optimizer the same behavior as our existing 8i. We plan to set: optimizer_feature_enable=3D8.1.7 after the migration. Maybe compatible=3D8.1.7 also.

I have two questions here:
1. For SQLs using RBO, the plan for the existing SQL won''t change, right? As oracle says no change for RBO since oracle 7.3. 2. For SQLs using CBO(as some feature will force CBO parsee), when the optimizer_feature_enabled=3D817, and don't change any optimizer_related parameters, is it still possible for SQL to choose different plan in 9i as the old plan in 8i? (Maybe because of different Cost caculation in 9i?)

Can some one with experience from 8i-9i share your experience? Thanks

--=20

Regards
Zhu Chao
www.cnoug.org
--

http://www.freelists.org/webpage/oracle-l Received on Mon May 09 2005 - 05:48:58 CDT