Communication takes place via network connections between SAP© and the MES system, which are setup in customizing. Depending on the use case, communication works via
- SAP© IDocs (in this case SAP© ensures the actual transfer of data),
- direct writing to files in a network folder or
- direct and indirect RFC Connections.
Decisive for the choice of connection are the actuality requirements for the data, that has to be exchanged.
We distinguish one- and two-dimensional communication connections. Data transfers from SAP© to MES and from MES to SAP© with a definite leading system are considered one-dimensional. Two-dimensional communication paths with alternating leading systems are used in the order change process and the functions of the availability check.
Files in network folders, that are used for data transfers, are constantly filled with data (append) by the sending system and are read out and processed by the receiving system. It is ensured, that there are no collisions (simultaneous "open" for processing) or double processing of data.
To start the processing in the receiving system, the transfer file is locked and copied to a processing file; the data in the transfer file is then deleted and the file is unlocked. Then processing of data starts from the processing file. The objective is here to keep the file lock as short as possible and to free the file immediately for further transfers.
All transferred and processed data are logged in a log file with timestamps and processing status. In the future I4 module, it will be possible to use this log file to monitor all traffic with status, to analyze errors (together with the customizing protocol) and, if necessary, to repeat a data transfer, if the application environment of the participating systems permit this.