I can't connect to a second instance of the database (Sybase, Oracle, etc.)

A single APPX session cannot connect to two instances of a database within the same APPX session. In other words, if an APPX session connects to one Oracle or Sybase database to access one or more tables, that same session will not be able to connect to a second Oracle database to access one or more additional tables. This is true for all supported databases.