Re: Analyzed Schema

In my experience, once you get to Oracle8, CBO is generally better than RBO overall. There are still a few exceptions, but very few. So, you should move towards CBO to improve performance and only use RBO selectively when tuning problem queries.

In terms of RBO going away, clearly it will not until Oracle starts using CBO for the data dictionary.

Marc Perkowitz
MTP Systems Consulting

In a message dated 10/19/00 8:27:51 AM Central Daylight Time, lkoivu_at_qode.com writes:

<< Subj: RE: Analyzed Schema
 Date: 10/19/00 8:27:51 AM Central Daylight Time  From: lkoivu_at_qode.com (Koivu, Lisa)
 Sender: root_at_fatcity.com
 Reply-to: ORACLE-L_at_fatcity.com
 To: ORACLE-L_at_fatcity.com (Multiple recipients of list ORACLE-L)    

 Hi Kirsten,  

 We are a perfect example. Our app runs RBO, and it runs fine. The task of  going to true CBO and putting stats on the database has been brought up, but  my reaction has been 'why fix something that isn't broken?' It would be a  painful task with a whole load of code-tuning to do, and explaining (and  defending) the optimizer to developers. De-support of RBO has been brought  up - but how long has Oracle been saying that? Forever.  

 My last position was a different story. With a data warehouse/data mart,  it's imperative to have as good statistics as you can afford (time-wise) in  order to take advantage of the optimizer's DW functionality. Bad statistics  will send your performance down the tubes.  

 The only thing I REALLY miss is being able to get good info out of the data  dictionary - I know we have chained rows in one of our largest tables (the  test databases do). However, I'll never really know for sure because I  can't analyze the table. Even a light estimate takes an unacceptable amount  time.  

 Others may have more convincing reasons.  

 HTH
 Lisa    

 -----Original Message-----
 Sent: Thursday, October 19, 2000 10:01 AM  To: Multiple recipients of list ORACLE-L    

 Hi all,  

    Are there situations where it is best to work without an analyzed  schema, or should all schema's be analyzed an a regular basis ?  

    Or : What are the pro's and con's of analyzing a schema ??? Received on Fri Oct 20 2000 - 09:11:44 CDT