optimizer_adaptive_features = FALSE - After upgrading to Oracle Database 12c, many PeopleSoft customers have noticed overall performance degradation which is related to Oracle 12c Optimizer Adaptive Feature (OAF). It is recommended that this value be disabled in all Oracle Databases running PeopleSoft Applications.
As stated, the parameter in Oracle 12.1 that controls Adaptive features is: OPTIMIZER_ADAPTIVE_FEATURES.
In Oracle 12.2, that parameter is obsolete and it is now controlled by two separate parameters: OPTIMIZER_ADAPTIVE_PLANS, OPTIMIZER_ADAPTIVE_STATISTICS.
NOTE: If you apply patch 22652097 to a 12.1.xx database, it will “split” OPTIMIZER_ADAPTIVE_FEATURES into the two separate parameters that 12.2 uses.
The parameter can be dynamically changed and set at the session level as well (no restart required!).
If you’re struggling with performance issues after a 12c upgrade, try disabling the adaptive features to see if it helps.
After disabling OPTIMIZER_ADAPTIVE_FEATURES, PeopleSoft performance was excellent and we had no more end user complaints.
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