As far as I see it is not recommended, but you should check the moodle docs..
generally slow, and hardly any core Moodle developers use it for development. -> Unless you are being forced somehow to use Oracle, we recommend Postgres or MariaDB for new Moodle installations.
There you will see Oracle.. Installation document is there..
https://docs.moodle.org/403/en/Installing_MoodleThey say: Moodle will technically work on Oracle, as it's supported by our database framework and it passes our basic unit testing. But! They also say: we do not recommend it for any new installations because it is
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