Synchronous and Asynchronous Communication
Communication between two systems can be basically split into two types: Synchronous and asynchronous communication. Both forms of communication have specific advantages and disadvantages, relating to either the business application or the system administration.
Synchronous Communication
Synchronous communication uses a single function call. Prerequisite for this is that at the time the call is made (or the message is sent), the receiving system is also active and can accept the call and further process it if necessary.
· Advantage: Synchronous communication can be implemented in function calls that require the immediate return of data to the sender system.
Example: You create a purchase order with account assignment in the sender system, and you want to perform a budget check in central accounting before you save the purchase order.
· Disadvantage: You need to ensure that both systems are active and can be contacted. If they are not, this can lead to serious disruption of processes. In particular, problems can arise if the receiving system is not available for long periods of time due to maintenance (for example, for a system upgrade).
Asynchronous Communication
For asynchronous communication, the receiving system does not necessarily have to be available at the time a function call is dispatched from the sender system. The receiving system can receive and process the call at a later time. If the receiving system is not available, the function call remains in the outbound queue of the sending system, from where the call is repeated at regular intervals until it can be processed by the receiving system.
· Advantage: The receiving system does not have to be available at the time the function call is made. If the system is unavailable for a long period of time, for example, for an upgrade, it can still process the data that has been sent in the interim at a later time, and processes in the sending system remain unharmed.
Example: You are sending a purchase order to a vendor system. The sending system cannot influence the availability of the receiving system. If the receiving system is not available, the purchase order can be sent repeatedly until the vendor system is available again.
· Disadvantage: Processes that require an immediate response to the sender system cannot be executed using this method.
