In my previous organization, after upgrading the databases from Oracle 9i to 10g, we had a few performance issues.
In Oracle 9i, some Queries used to give full reasults in few minutes but the same queries were taking too long in upgraded database (Oracle 10g).
After setting OPTIMIZER_FEATURES_ENABLE to 9.2.0, most of the performance
issues were resolved as it kept the release 9.2.0 optimizer behavior. and worked
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