Thread:Project:Support desk/Multiple Mediawiki Instances - Problems with Hoster/reply

Databases need to be on the same server because tables of the wiki and shared db are used on the same query, so they need the same connection.

Having different users for each database is not a problem. However, shared tables need to be accessible from the original wiki, which means you need to add permissions to the database user accessing the wiki database to at least read (and maybe update) on the shared tables of the shared database.