Here we are going to use CTU for CALL Transaction using and BI session for Batch Input Session method. Here are the main differences and comparisons between these two methods of BDC.
In CTU BDC data is run by the ABAP statement CALL TRANSACTION. In BI session BDC data is saved in a database using function modules BDC_OPEN_GROUP, BDC_INSERT, BDC_CLOSE_GROUP and later processing by SM35 transaction or by programs RSBDCBTC or RSBDCSUB.
In CTU method only one transaction can be called, but in BI session method several transactions can be recorded in a session.
IN CTU method error handling should done by our ABAP programs and we need to code for that. Bit in BI session method built in error handling mechanism is there.
In CTU method we can choose the update mode, but in BI session method update mode is always Synchronous
Also Read : ABAP Tutorial Home page -> SAP BDC -> ABAP Transaction codes