BDC is used to transfer data from SAP to SAP system or from a non-SAP system to SAP system.It uses the normal Transaction codes to transfer the data. This method is used to transfer large amount data that is available in electronic form. There are two types of methods offered by SAP for BDC:
First method is called the “Classical Method”. In this method, the data that is read by the BDC program from a sequential dataset file is stored in a batch-input session. To run the transactions in the session, you need to execute the session. This method uses the function module BDC_OPEN, BDC_INSERT and BDC_CLOSE to generate the sessions
In the second method, BDC uses the ABAP statement CALL TRANSACTION USING statement to run a transaction. In this method, BDC does not create a session.
Both the above methods need a common data structure for storing the instructions and data for SAP transactions. This structure is defined as the BDCDATA in the dictionary
In the rest of material you will be introducted three methods of doing BDC; Creating a Session, Call Transaction and CALL Dialog method