Re: Cost Based Optimizier

On 17 Jul 1996 101707.2323_at_compuserve.com wrote:

>
> We have a 7.1.3.2.1 production system and have just ANALYZED all the
> tables and indexes.
> Since we have done this we are suffering with response times from queries
> that join two and more tables.

You can ran COST-based optimizer in two modes FIRST_ROWS and ALL_ROWS (default). FIRST_ROWS mode will try to minimize the time before the FIRST row of the output is found, while ALL_ROWS will try to minimize the time until ALL rows are found. In MY experience FIRST_ROWS almost always result in better performance (often better then RULE-based, almost always better then ALL_ROWS). You can switch from ALL-ROWS to FIRST_ROWS (and back)) by typing

ALTER SESSION SET OPTIMIZER_GOAL = first_rows;

Give it a try.

Gene Received on Mon Aug 05 1996 - 00:00:00 CEST