A unique code must be used for a communication process in order to guarantee the integrity of the data to be transferred. The receiving system can then use this code to decide whether this data has already been received and processed.
For example, communication may break down during data transmission when goods receipts are entered on mobile data entry devices. The person handling the data would then have to send it again to make sure that it is posted in the SAP system. If, however, the data was successfully received and processed the first time it was sent to the SAP system, the system must be able to recognize this and then not process the second data record.
This example inevitably results in the following sequence of operations between the sending and receiving system.