The Adaptive Features is divided in two parts
- Adaptive Plans
- the possibility to change plans during execution
- Adaptive Statistics
- the statistics allow plans to be built from the results of previous executions
In 12.1 both components will be managed by the parameter „optimizer_features_enable“ and is per default on „TRUE“.
In 12.2 the parameter „optimizer_features_enable“ obsolete. The adaptive feature is now controlled by two parameters
- optimizer_adaptive_statistics default „FALSE“
- optimizer_adaptive_plans default „TRUE“
What are the recommendation for 126.96.36.199 if you do a upgrade. You should directly adopt the 12.2 default by applying the following Patches:
- Patch 22652097 splits the parameter optimizer_adaptive_features into two, as above, and disables adaptive statistics.
- Patch 21171382 disables the automatic creation of extended statistics unless the optimizer preference AUTO_STAT_EXTENSIONS is set to ON.
If you Upgrade to 12.1..2 set directly the Default for Oracle 12.2.
Yes, the next Upgrade to Release 12.2 came sooner or later.