Regarding: RFC Function Mod

Question

Hi all,
Can any body Tell me whats the Difference between Synchroner RFC and Asynchroner
All i KNow is that
Synchroner RFC
CALL FUNCTION func DESTINATION dest
                     parameter_list.
Asynchroner RFC
2. CALL FUNCTION func STARTING NEW TASK task
                [DESTINATION {dest|{IN GROUP {group|DEFAULT}}}]
                parameter_list
                [{PERFORMING subr}|{CALLING meth} ON END OF TASK].
Can any body Please explain ...
Thanks
Srinivas

Answer 1

hi,
A remote function call (RFC) is the call of a function module that runs in a different system to the calling program. Although 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 the same system.
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.
The RFC- interface system is made up of the following interfaces:
• Calling interface for ABAP programs
• Each ABAP program can call a remote function module using the command CALL FUNCTION...DESTINATION. The parameter DESTINATION informs the SAP system that the called function module runs in a different system to the calling system. RFC communication with the remote system takes place as a part of the CALL FUNCTION command.
• RFC function modules in an SAP system must be proper function modules and must be registered in the SAP system as remote.
• If the calling program and the called program are both ABAP programs, the RFC interface provides both communication partners. The calling program can be any ABAP program, and the called program must be a function module that is registered as remote.
• For more detailed information on calling function modules that are registered as remote, see Calling RFC Function Modules in ABAP.
• For more information on writing function modules that you want to call remotely, see Writing RFC Function Modules in ABAP.
• Interfaces for calling non-ABAP programs
If either the calling program or the called partner is not an SAP program, this program must be programmed in such a way that it can play the role of the other partner in RFC communication.
To support you when implementing RFC partner programs in non-SAP systems, read: Components of the SAP Communication Technology
RFC-supported and GUI-supported interfaces can be used by external programs to call function modules in SAP systems, and execute them in these systems. Likewise, ABAP programs can also use these interfaces to use functions supplied by external programs.
These are the types of RFC :
Asynchronous RFC (aRFC)
Synchronous RFC (sRFC)
Transactional RFC (tRFC)
Queued RFC (qRFC)
Parallel RFC (pRFC)
RFC:
Remote Function Call (RFC) is the standard SAP interface for communication between SAP systems. The RFC calls a function to be executed in a remote system.
Asynchronous RFC :
This is used when you need to increase the performance of ABAP program by having system call more than one function module in parallel than forcing the program to wait for results .
Synchronous RFC:
The first version of RFC is synchronous RFC (sRFC). This type of RFC executes the function call based on synchronous communication, which means that the systems involved must both be available at the time the call is made.
Transactional RFC:
If an error occurs during a synchronous remote function call, the system cannot tell at what point the error occurred (most crucially, whether the function module was actually processed in R/3 before the operation failed). Restarting a failed call is therefore a dangerous thing to do, since you risk duplicating a completed function call.
To alleviate this problem, you can use transactional RFC, which guarantees that each function call you issue will only be executed once, even if you submit it repeatedly to the R/3 System. The system implements this safeguard by assigning a unique transaction ID (TID) to each transaction that you submit. When you attempt to process the transaction, the system checks whether that TID has already been processed. If it has, the transaction is ignored.
Queued RFC:
When you use transactional RFC, you cannot guarantee the order in which the function calls will be processed in the system (it is quite possible that one call might overtake another). For cases where you need to specify a particular processing order, you can use queued RFC, which is an extension of transactional RFC. In qRFC, you place each function call in a logical queue. A function call cannot be executed until all of its predecessors in the queue have been processed. Queued RFC calls are processed asynchronously.
For More Info,
https://www.sdn.sap.com/irj/sdn/go/portal/prtroot/docs/library/uuid/f078394a-4469-2910-c4bf-853c75674694