Oracle 10 optimizer from RULE to COST: why?

Question

Oracle decided to dismiss the rule-based optimizer from version 10g, leaving the cost-based one as the only choice.

I think that a rule-based optimizer has the unv

Answer 1

The reason they moved to cost-based optimization is that it can perform better since its based on analyzing statistical information that the rule-based optimizer does not have.

To make the CBO work better, its important to understand the role that statistics gathering plays in execution plan changes which directly affect performance. For one thing, running statistics more or less frequently could help you. Here is a good article about the CBO and statistics:

Optimizing Oracle Optimizer Statistics