• Default type when you call a function module via RFC.

• The caller program waits until the remote system has completed the function execution and returned the result.

• Example use: Real-time data retrieval (e.g., fetching stock from another SAP system).

• FM execution: CALL FUNCTION 'XYZ' DESTINATION 'SAP_R3'.

2. Asynchronous RFC (aRFC)

• Execution is non-blocking → Caller does not wait for immediate results.

• You can trigger parallel processing by calling multiple aRFCs at the same time.

• Example use: Mass data processing, parallelizing jobs.

• FM execution:

CALL FUNCTION ‘XYZ’ STARTING NEW TASK ‘TASKNAME’
DESTINATION ‘SAP_R3’
PERFORMING callback_form ON END OF TASK.

3. Transactional RFC (tRFC)

• Similar to aRFC, but with transactional reliability.

• Each call is executed exactly once in the target system (using LUWs – Logical Units of Work).

• Stored in SM58 until delivered successfully.

• Example use: Posting documents, ALE/IDoc communication.

• FM execution:

CALL FUNCTION ‘XYZ’ IN BACKGROUND TASK
DESTINATION ‘SAP_R3’.
COMMIT WORK.

4. Queued RFC (qRFC)

• Extension of tRFC, but ensures sequence/order of execution using queues.

• Uses inbound and outbound queues (transactions SMQ1/SMQ2).

• Example use: When sequence matters (e.g., stock transfer must happen before goods issue).

• FM execution: Similar to tRFC, but with queue configuration.

Summary :

So, depending on your scenario:

• Use sRFC for synchronous real-time calls.

• Use aRFC for parallel jobs.

• Use tRFC for reliable background communication.

• Use qRFC when sequence matters.

Types of Help Request:

1. Automatic Help (F1) from Data Element

   • Comes from documentation maintained in the data element.

   • No coding needed — just maintain the documentation in SE11.

2. Custom Help Request (Manual)

   • In module pool programs, you can write custom F1 help logic using PROCESS ON HELP-REQUEST.

Code :

*&---------------------------------------------------------------------*
*&---------------------------------------------------------------------*
*& Report ZPRG_TEST
*&---------------------------------------------------------------------*

REPORT zprg_test_ecc.

DATA :  it_help TYPE STANDARD TABLE OF helpval WITH HEADER LINE.

PARAMETERS : s_id TYPE ZAR_STUDENT_ID.

AT SELECTION-SCREEN ON s_id.
  SELECT SINGLE student_id FROM zar_student_data INTO @DATA(id).
  IF id IS INITIAL.
    MESSAGE 'Student ID not found' TYPE 'E'.
  ENDIF.

AT SELECTION-SCREEN ON HELP-REQUEST FOR s_id.
  CLEAR it_help[].

  it_help-tabname = 'bkid'.
  it_help-fieldname = 'Student_ID'.
  it_help-keyword = 'Description'.
  it_help-length = 150.
  it_help-value = 'Enter a student id or refer table ZAR_STUDENT_DATA to find student id'.

  APPEND it_help.

  CALL FUNCTION 'HELP_GET_VALUES'
    EXPORTING
      popup_title = 'About s-id'
    TABLES
      fields      = it_help
    EXCEPTIONS
      no_entries  = 1
      OTHERS      = 2.

  IF sy-subrc <> 0.
* Implement suitable error handling here
  ENDIF.

START-OF-SELECTION.

  SELECT * FROM zar_student_data INTO TABLE @DATA(lc_it_zlib) WHERE STUDENT_ID = @s_id.

  LOOP AT lc_it_zlib INTO DATA(wa_zlib).
    WRITE (22) : wa_zlib-student_id, wa_zlib-student_fname.
    SKIP.
  ENDLOOP.