The OpenTunnel Designer database interface software program for a particular database package — for example, Oracle — is sometimes called the database server. The server model defines the interaction between OpenTunnel Designer, the database package, and the database server. Unless you are developing database applications for OpenTunnel Designer, you need not be familiar with the details of the server model. It is sufficient to be aware that in the server model, database functions are separated from graphics functions. This means memory requirements for OpenTunnel Designer sessions are reduced when a database is not connected (a server is not loaded).