BDC and LSMW are the two data migration techniques (from legacy to SAP). BDC technique is usually done by ABAPers. It consists of three methods.
1) Call Dialog Method
2) Session Method
3) Call Transaction Method
In the case of Session Method ,a BDC Session is created , which has the data and info to run it in batch mode. When the user runs this session, every transactions are run in batch mode and tables are updated.
WHile in call transaction, no session is created. Instead , a report prog is created , which takes input from the file and calls the transaction in Batch mode.
Call dialog method is similar to call transaction, except that updation is done by the calling program itself. This method is obsolete.
Advantages of Batch Input Method are
1) Can process large data volumes
2) data integrity is maintained
LSMW and BDC are vastly different.
BDC (Batch Data Communication) is a technology used for data transfer. it is meant for transferring data thru SAP transactions itself. when u use BDC for data transfer, the sequence of steps is the same as when u use standard sap transaction screens for data upload. the only difference is that u can use different options for foreground/backgrou nd processing.
LSMW on the other hand is a tool that helps migrate data from a legacy system (non-sap system ) to SAP system. it offers u various options to use either batch input, direct input, BAPIs or idocs. it involves a series of some 17-18 steps to migrate data.
Batch Data Communication (BDC) is the process of transferring data from one SAP System to another SAP system or from a non-SAP system to SAP System.
BDC is an automatic procedure.
This method is used to transfer large amount of data that is available in electronic medium.
BDC can be used primarily when installing the SAP system and when transferring data from a legacy system (external system).
BDC uses normal transaction codes to transfer data.
Types of BDC :
CLASSICAL BATCH INPUT (Session Method)
BATCH INPUT METHOD:
This method is also called as ‘CLASSICAL METHOD’.
Synchronous Processing in database update.
Transfer data for more than one transaction.
Batch input processing log will be generated.
During processing, no transaction is started until the previous transaction has been written to the database.
Read more about Differences between LSMW and BDC
CALL TRANSACTION METHOD :
This is another method to transfer data from the legacy system.
Synchronous processing. The system performs a database commit immediately before and after the CALL TRANSACTION USING statement.
Updating the database can be either synchronous or asynchronous. The program specifies the update type.
Transfer data for a single transaction.
Transfers data for a sequence of dialog screens.
No batch input processing log is generated.
The LSM Workbench is an R/3-based tool that supports You when transferring data from non-SAP systems ("Legacy Systems") to R/3 once or periodically.
The tool supports conversion of data of the legacy system in a convenient way. The data can then be imported into the R/3 system via batch input, direct input, BAPIs or IDocs.
Furthermore, the LSM Workbench provides a recording function that allows to generate a "data migration object" in an entry or change transaction.
The main advantages of the LSM Workbench:
• Part of R/3 and thus independent of individual platforms
• A variety of technical possibilities of data conversion:
• Data consistency due to standard import techniques:
BAPIs (Business Application Programming Interfaces)
IDocs (Intermediate Documents)
The import technique to be used in an individual case depends on the business object.
• Generation of the conversion program on the basis of defined rules
• Clear interactive process guide
• Interface for data in spreadsheet format
• Creation of data migration objects on the basis of recorded transactions
• Charge-free for SAP customers and SAP partners