BDC allows you to perform database updates in the background using standard SAP transactions. The resultant entries will be as if the user had manually entered the data via SAP. This means that you do not bypass any of the standard SAP consistency checks, authorisations etc. There are two main methods of ABAP BDC, these are call transaction and batch input.
Batch Data Communication.
It is mainly used for uploading data into the SAP R/3 system. BDC works by simulating the user input from transactional screen via an ABAP program.
Normally, the tcode SHDB will be used to record the transaction code the user used. After, the simulation, the Abaper can generate a sample program and modify from there. It makes the programming easier and faster.
call transaction
BDC using the SAP Call transaction involves calling an SAP transaction in the background from within the ABAP program. The process involves building an Internal BDC table containing the screen information needed to execute the required transaction and then passing this to the Call transaction command
Batch input
The data input data file will come in the form of a flat file which the user save as file type txt file or prn file from the Microsoft Excel program. An Abaper will create a program to read the text file and upload into the SAP system
TO CREATE BDC CLICK ON BELOW LINK.
http://www.saptechnical.com/Tutorials/ABAP/BDC/withoutBDC.htm
