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

Because everything you can do with RBO, can be done with CBO.

The CBO can be rule based too — more than that, you may decide the "rules" yourself.

To create your own "rules", you hint your query or do a CREATE OUTLINE which will hint it for you. As a result, you execution plan is stable.

The outlines are stored in a system schema called OUTLN, they are editable.

As for me, I always supply hints to my queries running in a production database.