What are the methods to migrate data from a legacy system to SAP?

LSMW is used for migrating data from a legacy system to SAP system, or from one SAP system to another.

Apart from standard batch/direct input and recordings, BAPI and IDocs are available as additional import methods for processing the legacy data.

The LSMW comprises the following main steps:

  • Read data (legacy data in spreadsheet tables and/or sequential files).
  • Convert data (from the source into the target format).
  • Import data (to the database used by the R/3 application.
But, before these steps, you need to perform following steps :
  • Define source structure : structure of data in the source file.
  • Define target structure : structure of SAP that receives data.
  • Field mapping: Mapping between the source and target structure with conversions, if any.
  • Specify file: location of the source file
Of all the methods used for data migration like BDC, LSMW , Call Transaction which one is used most of the time?
How is the decision made which method should be followed? What is the procedure followed for this analysis?

All the 3 methods are used to migrate data. Selection of these methods depends on the scenario, amount of data need to transfer. LSMW is a ready  tool provided by SAP and you have to follow some 17 steps to migrate master data. While in BDCs Session method is the better choice because of some advantages over call transaction. But call transaction is also very useful to do immediate updation of small amout of data. (In call transaction developer has to handle errors).
SO Bottom line is make choice of these methods based of real time requirements.

These methods are chosen completely based on situation you are in. Direct input method is not available for all scenario, else, they are the simplest ones. In batch input method ,you need to do recording for the transaction concerned. Similarly, IDoc, and BAPI are there, and use of these need to be decided based on the requirement.

Try to go through the some material on these four methods, and implement them.  You will then have a fair idea about when to use which.

Explain the exact difference between lsmw & bdc.

BDC- It is Batch data communication. Its used for data conversion from legacy system to SAP system. Only technical people can do it. Tcode is SHDB.

LSMW- It is legacy system migration workbench. Its also used for data conversion from legacy system to SAP system. But it is role of functional consultant. 

There are 14 steps in LSMW. As soon as you complete the one step, automatically it will go to next step.

In general you can use LSMW. But if you want to transfer more than 40,000 data, then it is not possible in LSMW. That time you can take help of BDC.                                                           *-- Purnimarani Satapathy

LSMW Steps
LSMW Steps For Data Migration

SAP Data Migration Reference Book
Data Transfer Made Easy 4.0B/4.5x
This guidebook is particularly useful when performing data transfer from legacy systems to the R/3 System.

SAP Books
SAP Certification, Interview Questions, ABAP Programming, Functional and Basis Component Reference Books

Migrating SAP Data Tips
SAP Data Migration with LSMW

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SAP Basis, ABAP Programming and Other IMG Stuff
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