For those interested in the Big Daddy of DBMS, there are five new topics in the Databases chapter of the User Manual showing a complete install of IBM Db2. That rounds out the Big 5 DBMS topics in the User Manual, for MySQL, SQL Server, Oracle, PostgreSQL, and Db2.
Db2 for Developers allows completely free, "no strings attached" commercial and production use of DB2 with a limitation of 100 GB of storage, 16 GB of RAM and 4 cores, including all the high end features of the full enterprise Db2 configurations. That's much more storage than Oracle or SQL Server allow in their free versions, but uploads into Db2 of drawings (for now) are not convenient compared to the other DBMS servers.
That's likely to change in the months ahead, but until that happens I'd advise regarding Db2 use with Manifold as primarily leveraging any Db2 installations your organization already may have, as opposed to starting up and populating new Db2 installations with drawings.
On the plus side, 100 GB of storage is a lot for tables in classic DBMS work, and Manifold works absolutely super and seamlessly with Db2 for SQL and tables and such, so for classic DBMS work and learning about big-time DBMS packages the free Db2 package is a great tool.