From Release 3.0 onwards an RFC client program can call a function module in an SAP system without specifying the application server for establishing the connection. In an SAP system it is therefore possible to make use of load-balancing for RFC as well, a feature initially introduced for SAPGUI connections. This is done by means of the two functions RfcOpen or RfcConnect , or, as of 4.0, by RfcOpenEx : The system first builds up a connection to the Message Server of the SAP system and tries to find the application server with the least load ( LOAD BALANCING principle ). On the basis of this information, the RFC library internally builds up the connection to the selected application server.
This load balancing feature has the following advantages:
The load in an SAP system is distributed to different SAP application servers. The RFC connection is always established to an application server with the least load.
Using load balancing, the RFC server will be determined at run time from the application servers available. Therefore, RFC connections are independent of a specific application server.
Only the host name of the SAP message server and its port number are required in the hosts and services file. Information about the Gateway, application server, system number for RfcOpen or sideinfo entry and entries for the application server and Gateway are no longer required there.