BDC programming

What is BDC programming? 

• Transferring of large/external/legacy data into SAP system using Batch Input programming. Batch input is a automatic procedure referred to as BDC(Batch Data Communications).The central component of the transfer is a queue file which receives the data vie a batch input programs and groups associated data into “sessions”.

There are 5 parts in a BDC program .Each part is executed one after another. 1) Selection screen is used with a parameter to input the text file of TYPE RLGRAP-FILENAME . Various function modules like KD_GET_FILENAME_ON_F4 can be used to read the file name at runtime or the filename can be defaulted by using DEAULT clause in the parameter statement. 2) Open the text file for input.If file fails to open (SY-SUBRC NE 0) then stop the program with a error message.     OPEN DATASET filename FOR INPUT IN TEXT MODE is used to open the file. 3)Loop through the dataset using a loop  statement like DO .. ENDDO with an EXIT statemenyt if no next record exists. and filling the work structure which will hold the data for a single transaction in each loop pass.    Filling the BDC TABLE of TYPE BDCDATA in the loop for every record(equivalent to transaction) in the data set.  Submit the internal table containing bdc data for each and every transaction (internal table of TYPE BDCDATA is submitted for each transaction until all the records in the dataset are read) using CALL TRANSACTION 'tr' USING I_bdcdata MODE 'N' UDATE 'S' .  DO   READ DATASET file INTO W_bdcdata    IF SY-SUBRC NE 0.     EXIT.    ENDIF.   PERFORM Fill_BDCDATA                                      PERFORM Submit_BDCDATA  ENDDO 4) Error handling when submission via CALL TRANSACTION fails ,either by using the internal table to be filled by the system messages which is of TYPE BDCMSGCOLS and can be specified in CALL TRANSACTION statement with the addition MESSAGES INTO .  Or error handling by sending the mail to a predefined recipient.  Or for each and every transaction that fails create a single BDC SESSION by using BDC_OPEN_GROUP function module and submitting the intenal bdc data table to it.  For each and every error a report should display them all at the end of the program so that the transacton in error can be identified.  The approach of opening a BDC SESSION is often used with an error report when an error occurs as all the transaction in error can be seen and executed in the session manager . 5)Clean up actions.  Here clean up actions are performed like closing the dataset with CLOSE DATASET command ,closing any error session if they were created using CLOSE_GROUP function module.and displaying the report . To fill the bdc data table we should have all the information associated with the screens used in the transaction and all the fields in those screens that will be filled by the CALL TRANSACTION statement.We can use BDC SESSION RECORDER  or Transaction Recorder(Transaction SHDB) to get the information on the screens and the fields. The data which is required to fill the internal table of TYPE BDCDATA is Program Name Screen Number Screen Begin Field Name Field Value Information on Field Name and Field Type can be used to create the structure that will be used to read records from the data set . While filling the Field value in BDCDATA table care should be taken for special fields like 'BDC_CURSOR',' BDC_OKCODE' Structure of BDCDATA tablePROGRAM   Name of program DYNPRO      Number of screen DYNBEGIN   If New screen begins value ='X' FNAM            Field Name FVAL             Field Value Structure of  BDCMSGCOLL MSGID          Message ID MSGTYP      MessageType MSGNR        Message Number MSGV1         1st placeholder MSGV2         2nd Place Holder NSGV3         3rd Placce Holder MSGV4         4th Place Holder   To see all the messages stored by the system in the BDCMSGCOLS table we can use LOOP AT .ENDLOOP command. Code to read internal table of type BDCMSGCOLS. TABLE T100 HAS FOLLOWING FIELDSSPRSL   TYPE SPRAS (Language) ARBGB  TYPE ARBGP (BUSINESS AREA) MSGNR  Message number (3C) TEXT       Message Text (Type 73C)  LOOP AT MESSTAB.     "Int Table of TYPE BDCMSGCOLS         SELECT SINGLE * FROM T100 WHERE SPRSL = MESSTAB-MSGSPRA                                   AND   ARBGB = MESSTAB-MSGID                                   AND   MSGNR = MESSTAB-MSGNR.         IF SY-SUBRC = 0.           L_MSTRING = T100-TEXT.           IF L_MSTRING CS '&1'.             REPLACE '&1' WITH MESSTAB-MSGV1 INTO L_MSTRING.             REPLACE '&2' WITH MESSTAB-MSGV2 INTO L_MSTRING.             REPLACE '&3' WITH MESSTAB-MSGV3 INTO L_MSTRING.             REPLACE '&4' WITH MESSTAB-MSGV4 INTO L_MSTRING.           ELSE.             REPLACE '&' WITH MESSTAB-MSGV1 INTO L_MSTRING.             REPLACE '&' WITH MESSTAB-MSGV2 INTO L_MSTRING.             REPLACE '&' WITH MESSTAB-MSGV3 INTO L_MSTRING.             REPLACE '&' WITH MESSTAB-MSGV4 INTO L_MSTRING.           ENDIF.           CONDENSE L_MSTRING.           WRITE: / MESSTAB-MSGTYP, L_MSTRING(250).         ELSE.           WRITE: / MESSTAB.         ENDIF.       ENDLOOP.       SKIP.     ENDIF.

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