SAP does not live in isolation. Every company that runs SAP also has other systems — CRM, e-commerce, legacy databases, third-party warehouses, custom mobile apps. And every company eventually migrates data from old systems into SAP when they go live.

This is where the three interface techniques you will learn in this chapter come in: BDC for bulk data upload, BAPI for standardized business operations, and IDoc for system-to-system data exchange.

🎯 What You Will Learn in This Chapter

• What BDC is and when to use it for data migration
• The difference between Session Method and Call Transaction
• How to record a BDC session using SHDB
• What a BAPI is and why it is upgrade-safe
• How to call a BAPI and commit changes with BAPI_TRANSACTION_COMMIT
• What an IDoc is and its three-part structure
• Common IDoc types and the role of ALE
• Different RFC types (sRFC, aRFC, tRFC, qRFC, bgRFC)
• How to upload and download files with GUI_UPLOAD / GUI_DOWNLOAD

📥 Technique 1: BDC (Batch Data Communication)

BDC is SAP’s technique for uploading large volumes of data by simulating user input on standard transactions. You record the steps a user takes, save them as a batch input session, and run the session to create thousands of records automatically.

When to use BDC

• Data migration — moving legacy data into a new SAP system during go-live
• Bulk uploads — loading thousands of records at once (customers, materials, vendors)
• When no BAPI exists — BDC works on any transaction, BAPI only where SAP provides one
• One-time data loads — initial setup of master data or transactional data

Recording a BDC session — SHDB

Session Method vs Call Transaction

Session Method — Code Example

" 1. Open the session
CALL FUNCTION 'BDC_OPEN_GROUP'
  EXPORTING
    client = sy-mandt
    group  = 'ZBDC_SESSION'
    user   = sy-uname
    keep   = 'X'.

" 2. Loop over source data
LOOP AT lt_data INTO DATA(ls_data).
  CLEAR lt_bdcdata.
  PERFORM add_bdc_field USING 'BDC_CURSOR' 'RMMG1-MATNR'.
  PERFORM add_bdc_field USING 'BDC_OKCODE' '/00'.
  PERFORM add_bdc_field USING 'RMMG1-MATNR' ls_data-matnr.
  " ... more fields ...

  CALL FUNCTION 'BDC_INSERT'
    EXPORTING
      tcode     = 'MM01'
    TABLES
      dynprotab = lt_bdcdata.
ENDLOOP.

" 3. Close the session
CALL FUNCTION 'BDC_CLOSE_GROUP'.

" 4. Run the session in SM35
" SM35 → Select session → Process → Foreground/Background

" Helper FORM to build BDC data
FORM add_bdc_field USING fname fval.
  DATA: ls_bdcdata TYPE bdcdata.
  ls_bdcdata-fnam = fname.
  ls_bdcdata-fval = fval.
  APPEND ls_bdcdata TO lt_bdcdata.
ENDFORM.

Call Transaction — Code Example

LOOP AT lt_data INTO DATA(ls_data).
  CLEAR lt_bdcdata.
  " Build bdcdata for this record
  PERFORM add_bdc_field USING 'BDC_CURSOR' 'RMMG1-MATNR'.
  PERFORM add_bdc_field USING 'BDC_OKCODE' '/00'.
  PERFORM add_bdc_field USING 'RMMG1-MATNR' ls_data-matnr.

  CALL TRANSACTION 'MM01'
    USING lt_bdcdata
    MODE 'N'                " N = no display, E = errors only, A = all screens
    UPDATE 'S'              " S = synchronous, A = asynchronous, L = local
    MESSAGES INTO lt_messages.

  " Check messages for errors
  LOOP AT lt_messages INTO DATA(ls_msg) WHERE msgtyp = 'E' OR msgtyp = 'A'.
    WRITE: / 'Error:', ls_msg-msgv1, ls_msg-msgv2.
  ENDLOOP.
ENDLOOP.

🔗 Technique 2: BAPI (Business API)

A BAPI is a standardized, RFC-enabled function module that exposes a business operation in SAP. Instead of simulating user input on a screen (like BDC), you call a documented, upgrade-safe function that performs the operation directly.

Why BAPIs are better than BDC

• Upgrade-safe — SAP guarantees BAPI interfaces across releases
• Documented — every BAPI has clear input/output parameters and return messages
• Remote-enabled — can be called from external systems via RFC/HTTP
• Standardized error handling — every BAPI returns a RETURN table with type, code, and message
• Business-level — you call “create customer”, not “fill screen 1, press enter, fill screen 2…”

Common BAPIs

Anatomy of a BAPI call

DATA: ls_header   TYPE bapimathead,
      ls_client   TYPE bapi_mara,
      ls_clientx  TYPE bapi_marax,
      lt_return   TYPE TABLE OF bapiret2.

" 1. Fill input structures
ls_header-material = 'ZTEST001'.
ls_header-ind_sector = 'M'.
ls_header-matl_type  = 'FERT'.
ls_client-base_uom = 'PC'.
ls_clientx-base_uom = 'X'.  " X marks the field as changed

" 2. Call the BAPI
CALL FUNCTION 'BAPI_MATERIAL_SAVEDATA'
  EXPORTING
    headdata       = ls_header
    clientdata     = ls_client
    clientdatax    = ls_clientx
  TABLES
    returnmessages = lt_return.

" 3. Check the return table
READ TABLE lt_return INTO DATA(ls_return)
  WITH KEY type = 'E'.
IF sy-subrc = 0.
  WRITE: / 'Error:', ls_return-message.
  CALL FUNCTION 'BAPI_TRANSACTION_ROLLBACK'.
ELSE.
  " 4. Commit only if no errors
  CALL FUNCTION 'BAPI_TRANSACTION_COMMIT'
    EXPORTING
      wait = 'X'.
  WRITE: / 'Material created successfully.'.
ENDIF.

📨 Technique 3: IDoc (Intermediate Document)

An IDoc is SAP’s standard container for exchanging business documents between systems. When SAP sends a purchase order to a supplier, when two SAP systems share customer master data, when SAP receives invoice data from a bank — that data travels as an IDoc.

The three-part structure of an IDoc

Common IDoc types

Key IDoc transactions

What is ALE?

ALE (Application Link Enabling) is SAP’s technology for distributing master and transactional data between SAP systems (or SAP and external systems) using IDocs. It is commonly used in:

• Central master data distribution (one system owns customer master, others receive it)
• Multi-system ERP landscapes
• SAP-to-SAP communication across modules
• SAP-to-SAP or SAP-to-third-party integrations

📡 RFC Types — How SAP Talks to Other Systems

RFC (Remote Function Call) is the protocol SAP uses to invoke function modules in remote systems. BAPIs typically use RFC for external calls.

📁 File Upload/Download — GUI_UPLOAD / GUI_DOWNLOAD

Most BDC and BAPI programs start with data from a file. Here is how to upload it.

Upload a file from the user’s PC

DATA: lt_raw_data TYPE TABLE OF string,
      lv_filename TYPE string.

" Ask user to select a file
CALL METHOD cl_gui_frontend_services=>file_open_dialog
  CHANGING
    file_table = DATA(lt_files)
    rc         = DATA(lv_rc).

READ TABLE lt_files INTO DATA(ls_file) INDEX 1.
lv_filename = ls_file-filename.

" Upload the file
CALL FUNCTION 'GUI_UPLOAD'
  EXPORTING
    filename   = lv_filename
    filetype   = 'ASC'
  TABLES
    data_tab   = lt_raw_data
  EXCEPTIONS
    file_open_error = 1
    OTHERS          = 2.

IF sy-subrc <> 0.
  MESSAGE 'Error opening file' TYPE 'E'.
ENDIF.

Download to the user’s PC

CALL FUNCTION 'GUI_DOWNLOAD'
  EXPORTING
    filename = 'C:\temp\report.xlsx'
    filetype = 'ASC'
  TABLES
    data_tab = lt_output.

📝 Chapter Summary

• BDC — simulates user input on standard transactions. Used for bulk data migration. Session Method processes in background (SM35); Call Transaction runs immediately.
• BAPI — standardized, upgrade-safe function modules that expose business operations. Always check the RETURN table.
• BAPI_TRANSACTION_COMMIT — required to save changes made by BAPIs. Without it, nothing is written to the database.
• IDoc — SAP’s container for system-to-system data exchange. Three parts: Control Record, Data Records, Status Records.
• ALE — SAP’s technology for distributing data via IDocs. Uses distribution models, partner profiles, and ports.
• RFC — protocol for remote function calls. Types: sRFC, aRFC, tRFC, qRFC, bgRFC.
• GUI_UPLOAD / GUI_DOWNLOAD — the standard way to move files between the user’s PC and SAP.
• Prefer BAPI over BDC for new development. Use BDC only when no BAPI exists.