We have a moodle 3.4 installation on windows 2012 server with mysql 5.7. We want to migrate the setup to Oracle 11G/12C without affecting the ongoing courses (of course downtime is allowed, but no data loss). How this can be done?
Although Moodle is in theory compatible with Oracle, you'll be pretty much on your own. Very few optional plugins will ever have been tested with it. It's a bad plan. The best advice I can give is to stick with the server platforms that everybody else uses. For your sanity.
To make matters worse - migrating from one DB to another is rarely plain sailing. There are some tools out there to do it, though.