In SAP ABAP, what is BDC programming and when is Batch Data Communication typically used?

Introduction / Context:
Batch Data Communication, commonly abbreviated as BDC, is one of the earliest and most traditional techniques for loading data into SAP systems. Although newer technologies such as IDocs, BAPIs, and migration tools exist, BDC remains an important concept in SAP interviews. Questions about BDC programming aim to assess whether a candidate understands how data migration can be performed by simulating online transactions with ABAP programs.

Given Data / Assumptions:

• We are considering classic SAP ERP or S/4HANA systems that still support BDC.
• BDC is used to import data from legacy or external systems by running SAP transactions programmatically.
• BDC can use either the session method or the CALL TRANSACTION method.
• The question is about the definition and typical use cases of BDC programming.

Concept / Approach:
BDC programming involves creating an ABAP program that fills a BDC data structure with control and field information for each screen of a target transaction. The program then either creates a batch input session or uses CALL TRANSACTION to run the transaction with that data. This simulates user input in a controlled and repeatable way, which makes it suitable for loading master data, open items, or other large data sets from non SAP systems. It is called batch data communication because it automates communication of data in batches between systems through the SAP transaction layer.

Step-by-Step Solution:
Step 1: In a BDC program, developers usually read input data from a file or an internal table that originates from a legacy or external system. Step 2: For each record, the program fills entries in an internal table of type BDCDATA, specifying transaction code, screen numbers, field names, and field values. Step 3: Depending on the chosen method, the program either creates a batch input session that will be processed later in SM35, or calls the transaction immediately with CALL TRANSACTION USING bdcdata. Step 4: SAP processes the BDC data as if a user were entering values on the screens, performing all validations and updates through the standard application logic. Step 5: This approach is widely used when no direct interfaces or BAPIs are available or when projects rely on recorded transaction flows. Step 6: Option a captures this definition, while options b, c, and d describe activities unrelated to data migration or transaction simulation.

Verification / Alternative check:
In SAP documentation, BDC is described as an interface technique that uses screen by screen data input. Tools like SHDB help create recording based BDC programs, demonstrating that BDC is about replaying transaction screens. Debugging a BDC program shows that it populates BDCDATA and calls transactions; nothing in the process compresses ABAP source code, designs dashboards, or replaces the operating system scheduler, which confirms that option a is correct.

Why Other Options Are Wrong:
Option b is wrong because ABAP transport compression is handled by the transport system and not called BDC programming. Option c is incorrect because dashboard design involves tools like SAP Analytics or Web Dynpro, not BDC. Option d is wrong because the SAP kernel and operating system scheduler are separate low level components that are not implemented in ABAP BDC logic.

Common Pitfalls:
A common pitfall is to use BDC for all data migration tasks, even when better interfaces exist. BDC can be fragile because changes in transaction screens may break recordings. Another issue is performance; poorly designed BDC programs can be slow and hold locks for long periods. However, understanding BDC programming remains important for maintaining legacy solutions and for answering interview questions that focus on classic SAP techniques.

Final Answer:
BDC programming is the technique of writing ABAP programs that simulate online transaction screens to transfer large volumes of data from legacy or external systems into SAP automatically.