RFC functionality between two SAP systems or between an external system and an SAP system has been available since Release 2.1 of the SAP system.
Up to Release 3.0 of the SAP system, RFCs are executed directly using the application server; in later versions, the load can be distributed across application servers by using a pre-activated message server.
The RFC offers a variety of “service qualities“. These are:
· Synchronous RFC
· Asynchronous RFC without further service promise
· Transactional RFC, which guarantees one-time execution and is offered as of Version 3.0
· Queue RFC, which guarantees one-time execution while assuring the call sequence and is offered as of Version 3.1.
In the R/2 system, function modules are available as a concept for modularizing ABAP programs as of Version 5.0. From Version 5.0D, function modules can also be called and executed remotely.
Destinations are stored and maintained in the R/2 System using the transaction SM59 in table TRFCD.
In the case of an RFC between an R/2 System in an IBM environment and another SAP system or external systems, an SAP Gateway must be running on a machine that supports SNA LU6.2 protocol for the IBM host. The SNA product must also be installed on this machine, and the SAP Gateway must be able to run in conjunction with this product. This is necessary, because some SNA products are not compatible on the same machines.
The following SNA products are currently supported:
· SNA services or SNA server on IBM-AIX systems
· SNAplusLink on HP-UX systems
· Communication Manager on OS/2
· SNA Server on Windows NT systems
· SNALink SNA peer-to-peer 8.0 on SUN systems
· TRANSIT-SERVER and TRANSIT-CPIC on SNI-SINIX systems.