Thought I'd give it a try. I installed Oracle 12c with a container DB and one PDB. The basic database install comes with 4.2.0 and after a day or two fiddling with it, I managed to get it to work with an embedded pl/sql gateway. The tricky part was getting the pdb to interact with the apex installation in de cdb. Then I applied the latest patch to get the version to 4.2.2, and everything went to hell in a handbasket. When executing the apxchpwd script I keep running into an error (ORA-04023: Object APEX_040200.WWV_FLOW_UTILITIES could not be validated or authorized), which I just cannot appear to solve. Somehow it also killed my (cdb) EM Express access on port 5500, as that no longer works either. I ended up deleting the plugin DB completely and recreating it using the dbca, but the error just comes back. I now want to uninstall Apex completely from the cdb as well, using the instructions I found here: Utilizing the Multitenant Architecture, but there a reference is made to a patch (16946990), that I do not find on the support site. So unless anyone here has any suggestions on how to continue, I'm throwing in the towel and sticking to Apex on Oracle 11g2. I will give 12c a try again when it matures some more, in my experience that means waiting for 12.2 ;-)