Question - What should be the approach for writing a BDC program?
Answer -
STEP 1: CONVERTING THE LEGACY SYSTEM DATA TO A FLAT FILE to internal table CALLED "CONVERSION".
STEP 2: TRANSFERING THE FLAT FILE INTO SAP SYSTEM CALLED "SAP DATA TRANSFER".
STEP 3: DEPENDING UPON THE BDC TYPE
i)call transaction(Write the program explicity)
ii) create sessions (sessions are created and processed.if success data will transfer).