By default, AcuConnect performs synchronous CALLs to remote applications. That is, the client application CALLs the remote application, then waits for a response back from the server. Only when the client receives a response from the server does the client application continue processing.
To perform asynchronous CALLs, you can CALL the C$ASYNCRUN library routine along with the remote application name. This routine is installed during normal AcuConnect installation. More information on C$ASYNCRUN can be found in To CALL the C$ASYNCRUN library routine.