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Oracle Has made public(thru OTN Network) The Top Presntation for All categories.

Most Popular Tech Sessions, Oracle OpenWorld San Francisco 2004

optimizing the Oracle Optimizer

Since Oracle Optimizer is a black box in terms of the decisions it makes (extended tracing is the only way to see that).
There are some parameters that always require tweaking t actually get the job done .
\Beware getting the job done doesnt mean the job is always done right.
: "compare "

Jonathan Lewis on 10g

Jonathan has a good article to justify the upgrade to 10g and look behind the hype of the new database.
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