We save(!!) this Source System and start the RFC Server on the DI side. Since version 3.2 of DataServices this rfc server is folded into the Management Console.
So we start the Management Console, expand to the new "SAP Connections" node and open the "RFC Server Interface" item. In the Configuration tab a new RFC Server is added so that it can register itself inside the SAP System with the given PROGRAM_ID.
To make the settings more obvious above screenshot hat the SAP Logon dialog settings and the External Source System screen pasted into it.
The RFC ProgramID is the one we used before when configuring the SAP BW External Soure System. Remember, this string here is case sensitive!!!
UserName/Password is the one used when logging in into SAP BW via the SAP GUI.
The SAP Application Server name is any application server listed at the bottom of the SAP Logon screen.
The Client (=the German "Mandant") is specified during the login process to SAP GUI, so the same screen as where you type username/password in SAP GUI.
And the System Number is obviously.
Finally the SAP Gateway hostname and service are required. Usually you type the Message-Server as SAP Gateway hostname and as Service Name the text "SAPGW" with the trailing System Number. The logic of the System Number is it represents a port, e.g. 50 means TCP/IP port 3350, where this SAP instance can be reached at, and this port has a service name in /etc/services called "SAPGW50".
But the true answer is, ask the SAP basis team, they know these settings.
Once the RFC Server is configured we can go back to the Status tab and start it.
To validate SAP BW can now talk to DataServices, the SAP BW dialog has the Connection Test button at the top. Click on that and in the status line it will say "Connection DI_SOURCE OK" at the status bar at the bottom and present a ping-like output next.