RE: _optimizer_cost_based_transformation=OFF risks

  • From: "Alvaro Jose Fernandez" <alvaro.fernandez@xxxxxxxxx>
  • To: <saqibz@xxxxxxxxxxx>, <oracle-l@xxxxxxxxxxxxx>
  • Date: Wed, 24 Oct 2007 18:18:29 +0200

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.



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



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