I finally managed to install and test patch 22652097 (PROVIDE SEPARATE CONTROLS FOR ADAPTIVE PLANS AND ADAPTIVE STATISTICS FEATURES). Actually, I installed and tested two patches. The first was installed on top of “Oracle Database Patch 23054246 – Database Patch Set Update 220.127.116.11.160719” (from now on, 18.104.22.168.160719 PSU). The second was installed on top of “Patch 24448103 – Database Proactive Patch 22.214.171.124.161018” (126.96.36.199.161018 PBP).
From a functional point of view, both patches provides the 12.2 configuration in 12.1 as I describe it in this post. In fact, the behavior of setting the (un)documented initialization parameters as well as all the default values are the same. I was able to find only two differences between 12.2 and a patched 12.1.
- In a patched 12.1 it is not possible to successfully executed an ALTER SESSION statement that modifies the OPTIMIZER_ADAPTIVE_FEATURES initialization parameter (it is in 12.2). If you try to do it, the database engine raises an ORA-02248 (invalid option for ALTER SESSION).
- In a patched 12.1 the AUTO_STAT_EXTENSIONS preference is not available (it is in 12.2). To have it, you have to install patch 21171382 (AUTO DOP COMPUTES A HIGH DOP UNNECESSARILY). However, note that I was only able to install and test it with the 188.8.131.52.160719 PSU. In fact, it is not compatible with the 184.108.40.206.161018 PBP. In my opinion, this is a major issue! I really do not understand why it is not part of patch 22652097. UPDATE 2016-12-22: as you can read in the comments, Stefan pointed out that there is a version of patch 21171382 that is compatible with the 220.127.116.11.161018 PBP. It is the one called “Oracle Database 12c Release 18.104.22.168.13DBEngSysandDBIM”. I was able to successfully test it.
My expectation is that, in the future, Oracle immediately provides patch 22652097 for all PSU and PBP. Actually, I even hope that Oracle includes it in future PBP. If this expectation will be fulfilled, I see no reason for not applying it. Otherwise, I would advise to stick with the undocumented initialization parameters.