In SAP ABAP, what does BDC stand for and how many main methods exist to implement BDC data transfer?

Introduction / Context:
Batch Data Communication is one of the earliest data migration and interface technologies in SAP. Interviewers frequently ask both for the full form of BDC and for the number and names of its main methods. This checks whether candidates have been exposed to classic migration techniques and know that BDC is implemented in ABAP using two basic approaches.

Given Data / Assumptions:

• BDC is part of the SAP application layer and uses screen based transaction simulation.
• The two main BDC methods are the session method and the CALL TRANSACTION method.
• Both methods use BDC data structures describing screens and fields.
• The question asks for both expansion of the acronym and the count of main methods.

Concept / Approach:
The term BDC stands for Batch Data Communication. It refers to programs that feed transaction screens with data in a batch like fashion. In the session method, BDC data is stored as a batch input session and processed later, typically through SM35. In the CALL TRANSACTION method, the transaction is executed immediately in the context of the calling program using the BDC data. These two methods are repeatedly highlighted in SAP training and certification material as the primary BDC techniques.

Step-by-Step Solution:
Step 1: Remember the standard teaching that there are two ways to use BDC: session method and CALL TRANSACTION method. Step 2: Session method creates a session in the database and runs it later as a background job, often used for large volume migrations. Step 3: CALL TRANSACTION method performs the migration online within the ABAP program, enabling immediate evaluation of messages and more flexible error handling. Step 4: Both methods use the BDCDATA internal table to specify screens and field values, and both execute standard transaction logic. Step 5: Option a spells out Batch Data Communication and correctly states that there are two main methods: session and CALL TRANSACTION. Step 6: Options b, c, and d introduce incorrect expansions and imaginary methods or purposes, so they do not match SAP terminology.

Verification / Alternative check:
SAP training material and many textbooks describe BDC as Batch Data Communication and explicitly list the two methods. Sample ABAP code often includes comments like method: session or method: CALL TRANSACTION. There is no official method called quick input, and BDC programs do not write directly to tables without transactions, which confirms that option a is accurate.

Why Other Options Are Wrong:
Option b is wrong because Background Data Controller is not a recognised SAP term and the method names are invented. Option c is incorrect because BDC does not bypass transactions to update tables directly; that would be dangerous and unsupported. Option d is wrong because Binary Data Compression is unrelated to SAP BDC and does not describe a transaction based migration technique.

Common Pitfalls:
A common pitfall is to forget that both methods rely on the same BDC data structure and to confuse BDC with other technologies like IDocs or BAPIs. Another mistake is to think that only sessions exist and to overlook CALL TRANSACTION, which is often better for small and medium volumes. Recognising the full form and the count of main methods is an easy way to score points in an SAP interview.

Final Answer:
BDC stands for Batch Data Communication and there are two main methods: the session method and the CALL TRANSACTION method.