RFC is an SAP protocol to handle communications between systems which simplifies the programming. A remote function call (RFC) is the call of a function module that runs in a different system to the calling program. It is also possible to call a function module in the same system as an RFC; normally RFCs are used when the caller and the called function module run in different systems. In the SAP system, these functions are provided by the RFC interface system. The RFC interface system enables function calls between two SAP systems, or between an SAP system and an external system. RFCs manage

1) Communication process

2) Parameter transfer

3) Errors.

RFC describes an interface to call the function. In RFC communications between two SAP systems, the calling system uses an RFC definition in the target system to access a specific function. The destination of an rfc call might be R/2 connection, R/3 connection, internal connections, logical connections (like to logical systems) or TCP/IP (external systems) connections.

There are five types of RFCs in SAP

1) Synchronous RFC (sRFC)

It requires that the target system is active when the RFC is made. This type of rfc is used for communication between different systems and between SAP Web AS and SAP GUI.

2) Asynchronous RFC (aRFC)

It doesn’t require the target system to be active when RFC is made. This is used for parallel processing jobs and for communication between different systems.

3) Transactional RFC (tRFC)

This is a variation of aRFC. The transactions are divided into steps and are processes step by step. This is an asynchronous transaction. This is helpful in scenarios where there is probability of network failure between the systems.

4) Queued RFC (qRFC)

This is a variation of tRFC. Here the individual steps are executed sequentially.

5) FastRFC

This is used for system internal communications. Interactions between J2ee engine in sap & the abap runtime environment in the same instance are done using these RFC. This type of RFC is possible only if both the source & target are on the same system.

The RFCs are managed using t-code sm59