RE: _optimizer_cost_based_transformation=OFF risks

It's hard to predict, unless you precisely focus on changed/degraded plans due to applying the OFF setting.

I would like to recommend instead, to wait (don't deactivate) until you apply the patch. CBT appears a very good thing. I'm yet on 9i on production customers (there is no cost there for unnesting, merging, etc.), and had to totally deactivate these *uncosted* unnesting transformations at session level, since there were only 1 case where the query went bad - and developers refused changed the app.

regards,

alvaro

>....and if anyone can share their experiences with similar issues(good,
bad >or ugly) after changing the
_optimizer_cost_based_transformation=OFF  

saqib

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