The active database and all its data sets are closed automatically when user opens another database or closes the application.
To close active database (and all its data sets) manually, choose Database | Close menu or click the corresponding button.
To close an open data set manually, activate the corresponding window (page), right-click its title and choose Close Window (Page) menu.
If you connected to database under certain user name, then you can easily close current database and reconnect it as another user by double-clicking the User name line from database properties on General page:
See also