What are the major diff between the Rule base optimization and Cost Base Optimization?

In rule base optimization we use the Query to tune,but in cost base optimization we use the data retrieved by the query.

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Oct 29th, 2005
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Anurag Kehri

Jan 10th, 2006

Oracle having two mode of optimization.
1.Rule Based Optimizer(RBO).
2.Cost Based Optimization(CBO).
RBO is syntex driven,it uses basically a some kind of ranking system(20 condition ranking rule),called as a "Golden Rules".
to execute the query.
CBO is calculate the resource cost of each access path a choose the least expensive one,it is statical driven ,also uses the intelligent formula for calulating the cost of any SQL query after examine all the execution plan.
CBO having 80000+ combination for excuting any SQL query. By default Oracle 9i follows the CBO mode(choose).You can set it in session(useing alter session),or in instance level.
set optimization_mode =choose/rule