BDC and LSMW — Data Migration Techniques

The Data Migration Problem

When a company goes live on SAP (or migrates to S/4HANA), they need to load existing data — customers, materials, open orders, GL balances. This data comes from legacy systems in formats like CSV, Excel, or flat files.

The challenge: SAP transactions have complex validation rules, authorization checks, and workflow triggers. You can't just INSERT into database tables — that bypasses all business logic and leaves the system in an inconsistent state.

BDC solves this by simulating what a user would do: open a transaction, fill in fields, click buttons, and save. SAP processes each "session" as if a real user performed it, with all validations intact.

BDC — Batch Data Communication

Step 1: Record a Transaction with SHDB

Open transaction SHDB (Transaction Recorder) and create a new recording:

1. Enter a recording name (e.g., Z_CREATE_CUSTOMER)
2. Enter the transaction to record (e.g., XD01 — Create Customer)
3. Click "Start Recording"
4. SAP opens XD01. Fill in the fields as a normal user would.
5. Save the customer. The recording captures every screen, every field, every value.
6. Click "Back" to stop recording.

The recording produces a BDC table — a sequence of screen numbers, field names, and values:

Program          Screen    Field Name        Field Value
──────────       ──────    ──────────────    ──────────
SAPMF02D         0100      BDC_CURSOR        RF02D-KUNNR
SAPMF02D         0100      BDC_OKCODE        /00
SAPMF02D         0100      RF02D-KTOKD       0001
SAPMF02D         0110      BDC_CURSOR        KNA1-NAME1
SAPMF02D         0110      KNA1-NAME1        Acme Corp
SAPMF02D         0110      KNA1-SORTL        ACME
SAPMF02D         0110      KNA1-LAND1        US
...

Step 2: Create a BDC Program

REPORT z_bdc_customer_create.

DATA: lt_bdcdata   TYPE TABLE OF bdcdata,
      ls_bdcdata   TYPE bdcdata,
      lt_messages  TYPE TABLE OF bdcmsgcoll.

* Helper to add screen entries
FORM bdc_dynpro USING program TYPE any dynnr TYPE any.
  CLEAR ls_bdcdata.
  ls_bdcdata-program = program.
  ls_bdcdata-dynpro  = dynnr.
  ls_bdcdata-dynbegin = 'X'.
  APPEND ls_bdcdata TO lt_bdcdata.
ENDFORM.

* Helper to add field entries
FORM bdc_field USING fnam TYPE any fval TYPE any.
  CLEAR ls_bdcdata.
  ls_bdcdata-fnam = fnam.
  ls_bdcdata-fval = fval.
  APPEND ls_bdcdata TO lt_bdcdata.
ENDFORM.

START-OF-SELECTION.
  * Build BDC table for creating a customer
  PERFORM bdc_dynpro USING 'SAPMF02D' '0100'.
  PERFORM bdc_field  USING 'BDC_OKCODE' '/00'.
  PERFORM bdc_field  USING 'RF02D-KTOKD' '0001'.

  PERFORM bdc_dynpro USING 'SAPMF02D' '0110'.
  PERFORM bdc_field  USING 'BDC_OKCODE' '/00'.
  PERFORM bdc_field  USING 'KNA1-NAME1' 'TechMart Inc'.
  PERFORM bdc_field  USING 'KNA1-SORTL' 'TECHMART'.
  PERFORM bdc_field  USING 'KNA1-LAND1' 'US'.
  PERFORM bdc_field  USING 'KNA1-SPRAS' 'EN'.

  * ... more screens as captured in SHDB recording ...

  PERFORM bdc_dynpro USING 'SAPMF02D' '0300'.
  PERFORM bdc_field  USING 'BDC_OKCODE' '=UPDA'.  " Save

  * Execute the transaction
  CALL TRANSACTION 'XD01'
    USING lt_bdcdata
    MODE 'N'          " N = no display, A = display all, E = display on error
    UPDATE 'S'        " S = synchronous, A = asynchronous
    MESSAGES INTO lt_messages.

  * Check result
  IF sy-subrc = 0.
    WRITE: / 'Customer created successfully'.
  ELSE.
    WRITE: / 'Error creating customer'.
    LOOP AT lt_messages INTO DATA(ls_msg) WHERE msgtyp = 'E'.
      WRITE: / |Error: { ls_msg-msgid } { ls_msg-msgnr } { ls_msg-msgv1 }|.
    ENDLOOP.
  ENDIF.

BDC Modes

Mode    Behavior
─────   ─────────────────────────────────
'A'     Display All — shows every screen (for debugging)
'E'     Display on Error — shows screen only when an error occurs
'N'     No Display — runs in background (for production migration)

Always develop with mode 'A' (see every screen), test with 'E' (see errors), and run production migration with 'N' (fastest).

LSMW — Legacy System Migration Workbench

LSMW (transaction LSMW) is a wizard-based tool for data migration — no ABAP coding required. It provides:

1. Source structure — define the format of your legacy file (CSV, Excel)
2. Target structure — map to SAP fields
3. Field mapping — connect source fields to target fields with optional transformation rules
4. Recording — SHDB recording of the target transaction
5. Execution — read file, convert data, run BDC sessions in batch

LSMW is preferred by functional consultants who don't write ABAP. It's slower than custom BDC programs but requires no coding.

When to Use Which Technique

Technique    Best For                        Speed     Coding Required
──────────   ─────────────────────────────   ─────     ───────────────
BAPI         Creating business objects       Fast      Yes (ABAP)
BDC          Screen-based transactions       Medium    Yes (ABAP)
LSMW         Configuration-based migration   Medium    No
IDoc         System-to-system migration      Medium    Minimal
Direct Input SAP-provided programs           Fastest   No

BAPI is preferred when one exists for your scenario — it's faster and more reliable than BDC. BDC is necessary when there's no BAPI (many older transactions lack BAPIs). LSMW is for functional consultants doing one-time loads.

Key Takeaways

• BDC simulates user transactions — it fills screens and clicks buttons programmatically.
• Record transactions with SHDB to capture screen sequences and field names.
• Use CALL TRANSACTION for real-time processing, BDC sessions (SM35) for batch processing.
• LSMW is the no-code alternative for data migration — wizard-based, popular with functional consultants.
• Always prefer BAPIs over BDC when available — BAPIs are faster, more stable, and better for error handling.
• Develop in mode 'A', test in mode 'E', run production in mode 'N'.

Next Lesson

Module 5 is complete! You can build function modules, call BAPIs, communicate via RFC, exchange IDocs, and migrate data with BDC. In Module 6: Real-World Skills, we start with Lesson 28: Debugging ABAP Programs — the skill that separates junior developers from seniors.