BDC and LSMW Steps

Overview: How It Works
BDC Reports are used to transfer data from legacy system into SAP system during SAP Implementation. Based on the functional requirements you have to now write a BDC report to upload the legacy data into SAP system.
To Perform Data transfer, we will perform 3 tasks:
Task 1: Do a recording for the transaction by supplying sample data.
Task 2: Create an ABAP report based on the recording done.
Task 3: Now write ABAP code to fetch data from legacy system and store into SAP
System.

Steps in data transfer
1. Analysis and cleanup of data in the non-SAP system
2. Extraction of data from the non-SAP system
3. Mapping the data in SAP format
4. Transferring the data to the SAP System
5. Checking the data

Data Transfer Methods
Call transaction
Asynchronous processing takes place and the transaction is called every time.

Session method

Synchronous processing takes place and a session is prepared, which is to be handled through SM35. Moreover, in Batch Input processing system log is maintained for every transaction. In Call transaction method messages have to be captured at runtime.

Direct input

This is an SAP supplied conversion program that allows very fast loading of certain objects. The disadvantage is that it is not customizable.