4D v11 SQL introduced the Database Access File feature. Database Access Files have the extension 4DLINK.
As explained in previous assets (refer to the See Also links), a Database Access File can contain the user name and password of the 4D user to be logged into the database, thus bypassing the login dialog.
The same is true for merged client applications, however the user name and password must appear in a specific 4DLINK file since merged client applications cannot normally open an arbitraty 4DLINK file. This 4DLINK file is located in the "database" folder of the client application. It can be pre-created or, once the client has successfully connected to the server, it is automatically created. This file is named EnginedServer.4DLINK. The user name and password must be placed in this file.