When you install any of the Nuxeo products (DM, DAM, etc.) in their default configuration, they are set up to use the embedded H2 database engine. While H2 is perfectly acceptable for testing purposes, Nuxeo does not recommend that particular DB engine for production. For production servers, you have a number of choices for the backend database software, so it's up to you to install the basic database software package(s) before going any further.
Your choices in backend database software: