FAQ's BDC & LSMW

Question

Hi All please answer these Questions,
1.     What is BDC ?
2.     What is call transaction method ? what is the
syntax/procedure?
3.     What is session method and what is the
syntax/procedure?
4.     Difference between call transaction & session method?
5.     which of these methods can be best used in background
process?
6.     What is direct input method?
7.     How LSMW is advantageous than normal BDC?
8.     what are the steps in lsmw?
9.     IN LSMW can you use BAPI, ?
10.     Can you call a bdc from a report program?
11.     what is the difference between synchronus &
asynchronus methods?
12.     call transaction uses synchronus or synchronus method?
13.     session method uses synchronus or synchronus method?
14.     What is bapi?
15.     how bapi is different from call transaction/session?
16.     what r the advantages of bapi?
17.     for uploading master data(ex:customer data) into sap,
which methods you prefer? call
transaction/session/lsmw/bapi? why?
18.     tell any 2 standard bapi function modules used for
uploading sales order data?
Thnaks in advance
                                                                                Ranjith

Answer 1

Hi,
1.BDC is Batch Data Communication where data is transferred from legacy system to SAP system.
       Different methods of BDC are
         1. Call Transaction Method.
         2. Session Method
         3. Direct Input method.
2.  Call Transaction Method is  one of the method in BDC for Data Transfer.
     Syntax :
            CALL TRANSACTION trans [using bdctab MODE mode].
                Where trans = Transaction Code
                          Bdctab = Internal table of structure BDCDATA.
                          Mode = Display mode.
             Three possible entries are there for MODE.
                        A          -           Display all .
                        E          -           Display errors only.
                        N          -           No Display.
      Procedure :
             1.     Prepare a BDCDATA structure for the transaction that u wish 2 run.
             2.     With a CALL TRANSACTION USING statement,call the transaction and prepare the BDCDATA structure. For example:
                      CALL TRANSACTON ‘ZSRC’ USING BDCDATA MODE ‘A’.
                               MESSAGES INTO MESSTAB.
                       IF SY-SUBRC <> 0.
                        <Error_handling>.
                       ENDIF.
3.  Procedure :
             1.     Generate the batch input session using function module BDC_OPEN_GROUP.
             2.     The proceed as follows for each transaction that the session contains:
                          a . In the BDCDATA structure, enter the value for all screens and fields that must be processed in the transaction.
                          b. Use BDC INSERT to transfer the transaction and the BDCDATA structure to the session.
                           c.Close the batch input session with BDC CLOSE GROUP
                           d.Start to process the generated session.
4.Session method.
1) asynchronous processing.
2) can tranfer large amount of data.
3) processing is slower.
4) error log is created
5) data is not updated until session is processed.
Call transaction.
1) synchronous processing
2) can transfer small amount of data
3) processing is faster.
4) errors need to be handled explicitly
5) data is updated automatically
5.Call Transaction method.
6.Direct Input is a technique  which doesnot create a session but stores data directly.To enhance the batch input procedure, the system offers the direct input technique, especially for transferring large amounts of data.
7.In LSMW ,there are two more import techniques (BAPI,IDoc) & Mapping can be done automatically.It contains 17 to 18 steps for migrating the data.It's an automatic procedure.
8.Goto Transaction 'LSMW' and execute it.We can view the steps.
9.Yes,We can.There is an option in 'Maintaining Object Attributes'.
12.Synchronous processing.
    In Database Update,it may be Synchronous or Asynchronous.
13.Asynchronous processing.
    In Database Update,it is  Synchronous.
14.BAPI(Business Application Programming Interface) they are actually methods (business functions) exposed by the sap environment to manipulate business objects defined in the business objects repository. other sap or non sap systems can use these bapis for their business operations.
16: regarding advantages for BAPI, please refer: http://help.sap.com/saphelp_nw04/helpdata/en/7e/5e11dc4a1611d1894c0000e829fbbd/frameset.htm