hi friends,
Tel me a snenorio wher u should go for BDC , BAPI and LSMW....pls dont give technical defintions....pls suggest me the snerios.....
Thanks in advance...


SAP created the Business Framework to allow the technical integration and exchange of business data among SAP components and between SAP and non-SAP components. Important components of the Business Framework are the Business Application Programming Interfaces (BAPIs), which represent visible interfaces at the component boundaries and whose properties serve to integrate these components. 
The integration can include both components within a local network and components that are connected with one another through the Internet.
BAPIs allow integration at the business level, not the technical level. This provides for greater stability in the link, and independence from the underlying communication technology.
You can get all the standard SAP BAPI functions with the transactions code 'BAPI'.
Batch Data Communication or BDC is a batch interfacing technique that SAP developed.  It is mainly used for uploading data into the SAP R/3 system.   BDC works by simulating the user input from transactional screen via an ABAP program.
The data input data file will come in the form of a flat file which the user save as file type txt file or prn file from the Microsoft Excel program.  An Abaper will create a program to read the text file and upload into the SAP system.
Normally, the tcode SHDB will be used to record the transaction code the user used.  After, the simulation, the Abaper can generate a sample program and modify from there.  It makes the programming easier and faster. 
No ABAP effort are required for the SAP data migration.  However, effort are required to map the data into the structure according to the pre-determined format as specified by the pre-written ABAP upload program of the LSMW.
The Legacy System Migration Workbench (LSMW) is a tool recommended by SAP that you can use to transfer data once only or periodically from legacy systems into an R/3 System.
More and more medium-sized firms are implementing SAP solutions, and many of them have their legacy data in desktop programs. In this case, the data is exported in a format that can be read by PC spreadsheet systems. As a result, the data transfer is mere child's play: Simply enter the field names in the first line of the table, and the LSM Workbench's import routine automatically generates the input file for your conversion program.
The LSM Workbench lets you check the data for migration against the current settings of your customizing. The check is performed after the data migration, but before the update in your database.
So although it was designed for uploading of legacy data it is not restricted to this use.
We use it for mass changes, i.e. uploading new/replacement data and it is great, but there are limits on its functionality, depending on the complexity of the transaction you are trying to replicate.
The SAP transaction code is  'LSMW' for SAP version 4.6x.
For those with the older SAP version (4.7 and below), the data migration programs might not have been pre-loaded.
You can download the LSMW at no cost from SAPNet under Services, SAP Methodology and Tools, category Tools.
If you are an existing SAP customer with an OSS ID, you can access the SAP Service Marketplace to download the  LSWM for your Basis teams to install to your SAP system:
The LSM Workbench carries out the following tasks:
Reads the transfer data from one or more files (for example, spreadsheets, sequential files etc.)
Converts the data from the source format into the target format
Note that with background processing, the input file must not be located in the presentation server. Access to presentation server files is only possible when you are working online.