What is the key difference between synchronous and asynchronous RFC?

The distinction between synchronous and asynchronous Remote Function Calls (RFC) in SAP centers on how they handle communication between systems. Synchronous RFC requires a response from the called function before the calling program can proceed with further processing. This means that the execution of the subsequent code is dependent on receiving a result from the remote system, thus ensuring data consistency and immediate feedback on the operation performed.

In contrast, asynchronous RFC allows the calling program to continue executing without waiting for a response from the called function. This can be useful for operations where the result is not immediately needed, or where the calling system can continue tasks independently of the remote function's execution.

The characteristic of synchronous RFC being dependent on receiving a response before moving forward is essential for scenarios where immediate interaction and feedback are crucial, such as in transaction processing where the integrity of the operations is paramount.