ABAP Parallel Processing: aRFC, STARTING NEW TASK

Basic Concept

Method	Description
`STARTING NEW TASK`	Starts asynchronous RFC
`CALLING ... ON END OF TASK`	Callback on completion
`WAIT UNTIL`	Waits for results
`RECEIVE RESULTS`	Receives return values

Syntax

" Asynchronous call
CALL FUNCTION 'FUNC_NAME' STARTING NEW TASK task_name
  DESTINATION destination
  CALLING callback_method ON END OF TASK
  EXPORTING
    param = value
  TABLES
    itab  = lt_data.

" Wait for results
WAIT UNTIL lv_counter >= lv_expected.

" Retrieve results (in callback)
RECEIVE RESULTS FROM FUNCTION 'FUNC_NAME'
  IMPORTING
    result = lv_result
  TABLES
    itab   = lt_result.

Examples

1. Simple Asynchronous Call

REPORT zparallel_simple.

DATA: gv_result  TYPE string,
      gv_done    TYPE abap_bool.

START-OF-SELECTION.
  " Start asynchronous task
  CALL FUNCTION 'Z_LONG_RUNNING_TASK' STARTING NEW TASK 'TASK1'
    DESTINATION 'NONE'
    CALLING on_task_complete ON END OF TASK
    EXPORTING
      iv_input = 'Test'.

  " Wait for result
  WAIT UNTIL gv_done = abap_true UP TO 60 SECONDS.

  IF gv_done = abap_true.
    WRITE: / 'Result:', gv_result.
  ELSE.
    WRITE: / 'Timeout!'.
  ENDIF.

FORM on_task_complete USING p_task TYPE clike.
  RECEIVE RESULTS FROM FUNCTION 'Z_LONG_RUNNING_TASK'
    IMPORTING
      ev_result = gv_result.
  gv_done = abap_true.
ENDFORM.

2. Parallel Processing with Class

CLASS zcl_parallel_processor DEFINITION.
  PUBLIC SECTION.
    TYPES: BEGIN OF ty_task,
             id     TYPE i,
             status TYPE string,
             result TYPE string,
           END OF ty_task,
           ty_tasks TYPE STANDARD TABLE OF ty_task WITH KEY id.

    METHODS: run_parallel
      IMPORTING it_items       TYPE string_table
      RETURNING VALUE(rt_results) TYPE ty_tasks.

    METHODS: on_task_end FOR EVENT task_end OF cl_abap_parallel.

  PRIVATE SECTION.
    DATA: mt_tasks      TYPE ty_tasks,
          mv_completed  TYPE i,
          mv_total      TYPE i.
ENDCLASS.

CLASS zcl_parallel_processor IMPLEMENTATION.
  METHOD run_parallel.
    mv_total = lines( it_items ).
    mv_completed = 0.
    CLEAR mt_tasks.

    DATA(lv_task_id) = 0.

    LOOP AT it_items INTO DATA(lv_item).
      lv_task_id = lv_task_id + 1.

      APPEND VALUE #(
        id     = lv_task_id
        status = 'RUNNING'
      ) TO mt_tasks.

      " Asynchronous call
      CALL FUNCTION 'Z_PROCESS_ITEM' STARTING NEW TASK |TASK{ lv_task_id }|
        DESTINATION 'NONE'
        CALLING on_task_complete ON END OF TASK
        EXPORTING
          iv_item    = lv_item
          iv_task_id = lv_task_id.
    ENDLOOP.

    " Wait until all complete
    WAIT UNTIL mv_completed >= mv_total UP TO 300 SECONDS.

    rt_results = mt_tasks.
  ENDMETHOD.

  METHOD on_task_complete.
    DATA: lv_result  TYPE string,
          lv_task_id TYPE i.

    RECEIVE RESULTS FROM FUNCTION 'Z_PROCESS_ITEM'
      IMPORTING
        ev_result  = lv_result
        ev_task_id = lv_task_id.

    " Save result
    MODIFY mt_tasks FROM VALUE #(
      id     = lv_task_id
      status = 'COMPLETED'
      result = lv_result
    ) TRANSPORTING status result WHERE id = lv_task_id.

    mv_completed = mv_completed + 1.
  ENDMETHOD.
ENDCLASS.

3. Batch Processing with Chunks

CLASS zcl_batch_parallel DEFINITION.
  PUBLIC SECTION.
    CONSTANTS: c_max_tasks TYPE i VALUE 10.

    METHODS: process_in_batches
      IMPORTING it_data TYPE ty_data_tab
      RETURNING VALUE(rt_results) TYPE ty_result_tab.

  PRIVATE SECTION.
    DATA: mv_active_tasks TYPE i,
          mv_completed    TYPE i,
          mt_results      TYPE ty_result_tab.

    METHODS: on_batch_complete IMPORTING p_task TYPE clike.
ENDCLASS.

CLASS zcl_batch_parallel IMPLEMENTATION.
  METHOD process_in_batches.
    DATA: lt_chunk TYPE ty_data_tab,
          lv_chunk_size TYPE i,
          lv_task_no TYPE i.

    " Calculate chunk size
    lv_chunk_size = COND #(
      WHEN lines( it_data ) <= c_max_tasks THEN 1
      ELSE lines( it_data ) / c_max_tasks + 1
    ).

    mv_active_tasks = 0.
    mv_completed = 0.
    CLEAR mt_results.

    " Split data into chunks and process in parallel
    DATA(lv_start) = 1.
    WHILE lv_start <= lines( it_data ).
      lv_task_no = lv_task_no + 1.

      " Create chunk
      CLEAR lt_chunk.
      LOOP AT it_data INTO DATA(ls_data) FROM lv_start.
        APPEND ls_data TO lt_chunk.
        IF lines( lt_chunk ) >= lv_chunk_size.
          EXIT.
        ENDIF.
      ENDLOOP.

      " Start task
      CALL FUNCTION 'Z_PROCESS_BATCH' STARTING NEW TASK |BATCH{ lv_task_no }|
        DESTINATION 'NONE'
        CALLING on_batch_complete ON END OF TASK
        EXPORTING
          iv_batch_id = lv_task_no
        TABLES
          it_data = lt_chunk.

      mv_active_tasks = mv_active_tasks + 1.
      lv_start = lv_start + lv_chunk_size.

      " Limit max concurrent tasks
      IF mv_active_tasks >= c_max_tasks.
        WAIT UNTIL mv_completed > 0 UP TO 60 SECONDS.
      ENDIF.
    ENDWHILE.

    " Wait for all remaining tasks
    WAIT UNTIL mv_active_tasks = mv_completed UP TO 300 SECONDS.

    rt_results = mt_results.
  ENDMETHOD.

  METHOD on_batch_complete.
    DATA: lt_batch_results TYPE ty_result_tab.

    RECEIVE RESULTS FROM FUNCTION 'Z_PROCESS_BATCH'
      TABLES
        et_results = lt_batch_results.

    APPEND LINES OF lt_batch_results TO mt_results.
    mv_completed = mv_completed + 1.
  ENDMETHOD.
ENDCLASS.

4. Using Server Groups

DATA: lv_group TYPE rzlli_apts.

" Determine server group
CALL FUNCTION 'SPBT_INITIALIZE'
  EXPORTING
    group_name                     = 'parallel_generators'
  IMPORTING
    free_pbt_wps                   = DATA(lv_free_wps)
  EXCEPTIONS
    invalid_group_name             = 1
    internal_error                 = 2
    pbt_env_already_initialized    = 3
    currently_no_resources_avail   = 4
    no_pbt_resources_found         = 5
    cant_init_different_pbt_groups = 6
    OTHERS                         = 7.

IF sy-subrc = 0.
  lv_group = 'parallel_generators'.
ELSE.
  lv_group = 'parallel_generators'.  " Default group
ENDIF.

" Call with server group
CALL FUNCTION 'Z_HEAVY_CALCULATION' STARTING NEW TASK 'CALC1'
  DESTINATION IN GROUP lv_group
  CALLING on_calculation_done ON END OF TASK
  EXPORTING
    iv_param = lv_param.

5. Resource Management

CLASS zcl_resource_manager DEFINITION.
  PUBLIC SECTION.
    METHODS: get_available_processes
      RETURNING VALUE(rv_count) TYPE i.

    METHODS: process_with_throttling
      IMPORTING it_items TYPE string_table.

  PRIVATE SECTION.
    DATA: mv_max_parallel TYPE i VALUE 5,
          mv_running      TYPE i,
          mv_completed    TYPE i.
ENDCLASS.

CLASS zcl_resource_manager IMPLEMENTATION.
  METHOD get_available_processes.
    " Determine free work processes
    CALL FUNCTION 'SPBT_INITIALIZE'
      EXPORTING
        group_name                   = 'parallel_generators'
      IMPORTING
        free_pbt_wps                 = rv_count
      EXCEPTIONS
        OTHERS                       = 1.

    IF sy-subrc <> 0.
      rv_count = 3.  " Fallback
    ENDIF.

    " Limit maximum
    IF rv_count > mv_max_parallel.
      rv_count = mv_max_parallel.
    ENDIF.
  ENDMETHOD.

  METHOD process_with_throttling.
    DATA(lv_max) = get_available_processes( ).
    mv_running = 0.
    mv_completed = 0.

    DATA(lv_task_no) = 0.

    LOOP AT it_items INTO DATA(lv_item).
      lv_task_no = lv_task_no + 1.

      " Wait if maximum reached
      WHILE mv_running - mv_completed >= lv_max.
        WAIT UNTIL mv_completed > ( mv_running - lv_max ) UP TO 5 SECONDS.
      ENDWHILE.

      " Start task
      CALL FUNCTION 'Z_PROCESS_ITEM' STARTING NEW TASK |PROC{ lv_task_no }|
        DESTINATION 'NONE'
        CALLING on_item_done ON END OF TASK
        EXPORTING
          iv_item = lv_item.

      mv_running = mv_running + 1.
    ENDLOOP.

    " Wait for all
    WAIT UNTIL mv_completed >= mv_running UP TO 600 SECONDS.
  ENDMETHOD.
ENDCLASS.

6. Error Handling

CLASS zcl_parallel_with_errors DEFINITION.
  PUBLIC SECTION.
    TYPES: BEGIN OF ty_result,
             task_id TYPE i,
             success TYPE abap_bool,
             message TYPE string,
             data    TYPE string,
           END OF ty_result,
           ty_results TYPE STANDARD TABLE OF ty_result WITH KEY task_id.

    METHODS: process_with_error_handling
      IMPORTING it_items TYPE string_table
      RETURNING VALUE(rt_results) TYPE ty_results.

  PRIVATE SECTION.
    DATA: mt_results   TYPE ty_results,
          mv_completed TYPE i,
          mv_total     TYPE i.
ENDCLASS.

CLASS zcl_parallel_with_errors IMPLEMENTATION.
  METHOD process_with_error_handling.
    mv_total = lines( it_items ).
    mv_completed = 0.
    CLEAR mt_results.

    DATA(lv_task_id) = 0.

    LOOP AT it_items INTO DATA(lv_item).
      lv_task_id = lv_task_id + 1.

      TRY.
          CALL FUNCTION 'Z_RISKY_OPERATION' STARTING NEW TASK |RISK{ lv_task_id }|
            DESTINATION 'NONE'
            CALLING on_risky_complete ON END OF TASK
            EXPORTING
              iv_item    = lv_item
              iv_task_id = lv_task_id.

        CATCH cx_root INTO DATA(lx_error).
          " Document start error
          APPEND VALUE #(
            task_id = lv_task_id
            success = abap_false
            message = lx_error->get_text( )
          ) TO mt_results.
          mv_completed = mv_completed + 1.
      ENDTRY.
    ENDLOOP.

    " Timeout with error handling
    DATA(lv_start) = sy-uzeit.
    WHILE mv_completed < mv_total.
      WAIT UNTIL mv_completed >= mv_total UP TO 5 SECONDS.

      " Timeout check (5 minutes)
      IF sy-uzeit - lv_start > 300.
        " Mark remaining as timeout
        LOOP AT mt_results INTO DATA(ls_result) WHERE success IS INITIAL.
          ls_result-message = 'Timeout'.
          MODIFY mt_results FROM ls_result.
        ENDLOOP.
        EXIT.
      ENDIF.
    ENDWHILE.

    rt_results = mt_results.
  ENDMETHOD.
ENDCLASS.


" Callback with error handling
FORM on_risky_complete USING p_task TYPE clike.
  DATA: lv_result  TYPE string,
        lv_task_id TYPE i,
        lv_subrc   TYPE sy-subrc,
        lv_message TYPE string.

  RECEIVE RESULTS FROM FUNCTION 'Z_RISKY_OPERATION'
    IMPORTING
      ev_result  = lv_result
      ev_task_id = lv_task_id
    EXCEPTIONS
      communication_failure = 1 MESSAGE lv_message
      system_failure        = 2 MESSAGE lv_message
      OTHERS                = 3.

  IF sy-subrc = 0.
    APPEND VALUE #(
      task_id = lv_task_id
      success = abap_true
      data    = lv_result
    ) TO mt_results.
  ELSE.
    APPEND VALUE #(
      task_id = lv_task_id
      success = abap_false
      message = COND #( WHEN lv_message IS NOT INITIAL THEN lv_message
                        ELSE |Error { sy-subrc }| )
    ) TO mt_results.
  ENDIF.

  mv_completed = mv_completed + 1.
ENDFORM.

7. RFC Function Module for Parallelization

FUNCTION z_parallel_worker.
*"----------------------------------------------------------------------
*"*"Local Interface:
*"  IMPORTING
*"     VALUE(IV_TASK_ID) TYPE I
*"     VALUE(IT_DATA) TYPE TY_DATA_TAB
*"  EXPORTING
*"     VALUE(ET_RESULTS) TYPE TY_RESULT_TAB
*"     VALUE(EV_TASK_ID) TYPE I
*"----------------------------------------------------------------------

  ev_task_id = iv_task_id.

  LOOP AT it_data INTO DATA(ls_data).
    " Processing
    DATA(ls_result) = VALUE ty_result(
      id     = ls_data-id
      status = 'PROCESSED'
      value  = ls_data-value * 2
    ).
    APPEND ls_result TO et_results.
  ENDLOOP.

ENDFUNCTION.

8. CL_ABAP_PARALLEL for Modern Parallelization

CLASS zcl_modern_parallel DEFINITION.
  PUBLIC SECTION.
    INTERFACES: if_abap_parallel.

    CLASS-METHODS: run_parallel
      IMPORTING it_items TYPE string_table
      RETURNING VALUE(rt_results) TYPE string_table.

  PRIVATE SECTION.
    DATA: mv_item TYPE string.
ENDCLASS.

CLASS zcl_modern_parallel IMPLEMENTATION.
  METHOD if_abap_parallel~do.
    " This method is executed in parallel
    DATA(lv_result) = |Processed: { mv_item }|.

    " Serialize result
    p_out = cl_abap_parallel=>get_parallel_output( ).
    EXPORT result = lv_result TO DATA BUFFER p_out.
  ENDMETHOD.

  METHOD run_parallel.
    DATA: lt_instances TYPE TABLE OF REF TO zcl_modern_parallel,
          lt_handles   TYPE abap_parallel_handles.

    " Create instances
    LOOP AT it_items INTO DATA(lv_item).
      DATA(lo_instance) = NEW zcl_modern_parallel( ).
      lo_instance->mv_item = lv_item.
      APPEND lo_instance TO lt_instances.
    ENDLOOP.

    " Execute in parallel
    TRY.
        cl_abap_parallel=>run_parallel(
          EXPORTING
            i_instances = lt_instances
          IMPORTING
            e_handles   = lt_handles
        ).

        " Collect results
        LOOP AT lt_handles INTO DATA(ls_handle).
          IF ls_handle-done = abap_true.
            DATA: lv_result TYPE string.
            IMPORT result = lv_result FROM DATA BUFFER ls_handle-out.
            IF sy-subrc = 0.
              APPEND lv_result TO rt_results.
            ENDIF.
          ENDIF.
        ENDLOOP.

      CATCH cx_abap_parallel INTO DATA(lx_error).
        " Error handling
    ENDTRY.
  ENDMETHOD.
ENDCLASS.

9. Progress Indicator

CLASS zcl_parallel_progress DEFINITION.
  PUBLIC SECTION.
    METHODS: process_with_progress
      IMPORTING it_items TYPE string_table.

  PRIVATE SECTION.
    DATA: mv_total     TYPE i,
          mv_completed TYPE i,
          mv_errors    TYPE i.

    METHODS: update_progress.
ENDCLASS.

CLASS zcl_parallel_progress IMPLEMENTATION.
  METHOD process_with_progress.
    mv_total = lines( it_items ).
    mv_completed = 0.
    mv_errors = 0.

    DATA(lv_task_no) = 0.

    " Initialize progress indicator
    CALL FUNCTION 'SAPGUI_PROGRESS_INDICATOR'
      EXPORTING
        percentage = 0
        text       = |Starting { mv_total } parallel tasks...|.

    " Start tasks
    LOOP AT it_items INTO DATA(lv_item).
      lv_task_no = lv_task_no + 1.

      CALL FUNCTION 'Z_PROCESS_ITEM' STARTING NEW TASK |PROG{ lv_task_no }|
        DESTINATION 'NONE'
        CALLING on_progress_update ON END OF TASK
        EXPORTING
          iv_item = lv_item.
    ENDLOOP.

    " Wait and update progress
    WHILE mv_completed < mv_total.
      WAIT UNTIL mv_completed >= mv_total UP TO 1 SECONDS.
      update_progress( ).
    ENDWHILE.

    " Completion
    CALL FUNCTION 'SAPGUI_PROGRESS_INDICATOR'
      EXPORTING
        percentage = 100
        text       = |Done: { mv_completed } OK, { mv_errors } errors|.
  ENDMETHOD.

  METHOD update_progress.
    DATA(lv_percent) = mv_completed * 100 / mv_total.

    CALL FUNCTION 'SAPGUI_PROGRESS_INDICATOR'
      EXPORTING
        percentage = lv_percent
        text       = |{ mv_completed }/{ mv_total } processed ({ mv_errors } errors)|.
  ENDMETHOD.
ENDCLASS.

10. Map-Reduce Pattern

CLASS zcl_map_reduce DEFINITION.
  PUBLIC SECTION.
    TYPES: BEGIN OF ty_key_value,
             key   TYPE string,
             value TYPE i,
           END OF ty_key_value,
           ty_key_values TYPE STANDARD TABLE OF ty_key_value WITH KEY key.

    METHODS: map_reduce
      IMPORTING it_data TYPE string_table
      RETURNING VALUE(rt_result) TYPE ty_key_values.

  PRIVATE SECTION.
    DATA: mt_map_results TYPE ty_key_values,
          mv_map_done    TYPE i,
          mv_map_total   TYPE i.
ENDCLASS.

CLASS zcl_map_reduce IMPLEMENTATION.
  METHOD map_reduce.
    " MAP Phase - parallel
    mv_map_total = lines( it_data ).
    mv_map_done = 0.
    CLEAR mt_map_results.

    DATA(lv_chunk_no) = 0.
    LOOP AT it_data INTO DATA(lv_data).
      lv_chunk_no = lv_chunk_no + 1.

      CALL FUNCTION 'Z_MAP_FUNCTION' STARTING NEW TASK |MAP{ lv_chunk_no }|
        DESTINATION 'NONE'
        CALLING on_map_complete ON END OF TASK
        EXPORTING
          iv_data = lv_data.
    ENDLOOP.

    " Wait for all map tasks
    WAIT UNTIL mv_map_done >= mv_map_total UP TO 300 SECONDS.

    " REDUCE Phase - local (aggregate)
    DATA: lt_grouped TYPE SORTED TABLE OF ty_key_value WITH UNIQUE KEY key.

    LOOP AT mt_map_results INTO DATA(ls_result).
      READ TABLE lt_grouped ASSIGNING FIELD-SYMBOL(<fs_group>)
        WITH KEY key = ls_result-key.
      IF sy-subrc = 0.
        <fs_group>-value = <fs_group>-value + ls_result-value.
      ELSE.
        INSERT ls_result INTO TABLE lt_grouped.
      ENDIF.
    ENDLOOP.

    rt_result = lt_grouped.
  ENDMETHOD.
ENDCLASS.

11. Transactional Parallel Processing

CLASS zcl_transactional_parallel DEFINITION.
  PUBLIC SECTION.
    METHODS: process_and_commit
      IMPORTING it_items TYPE ty_item_tab
      RETURNING VALUE(rv_success) TYPE abap_bool.

  PRIVATE SECTION.
    DATA: mv_all_success TYPE abap_bool VALUE abap_true,
          mv_completed   TYPE i,
          mv_total       TYPE i.
ENDCLASS.

CLASS zcl_transactional_parallel IMPLEMENTATION.
  METHOD process_and_commit.
    mv_total = lines( it_items ).
    mv_completed = 0.
    mv_all_success = abap_true.

    DATA(lv_task_no) = 0.

    " Parallel processing (without commit)
    LOOP AT it_items INTO DATA(ls_item).
      lv_task_no = lv_task_no + 1.

      CALL FUNCTION 'Z_PROCESS_NO_COMMIT' STARTING NEW TASK |TRANS{ lv_task_no }|
        DESTINATION 'NONE'
        CALLING on_trans_complete ON END OF TASK
        EXPORTING
          is_item = ls_item.
    ENDLOOP.

    " Wait for all
    WAIT UNTIL mv_completed >= mv_total UP TO 300 SECONDS.

    " Commit or rollback
    IF mv_all_success = abap_true.
      CALL FUNCTION 'BAPI_TRANSACTION_COMMIT'
        EXPORTING
          wait = abap_true.
      rv_success = abap_true.
    ELSE.
      CALL FUNCTION 'BAPI_TRANSACTION_ROLLBACK'.
      rv_success = abap_false.
    ENDIF.
  ENDMETHOD.
ENDCLASS.

12. Practical Example: Mass Data Export

CLASS zcl_mass_export DEFINITION.
  PUBLIC SECTION.
    METHODS: export_customers_parallel
      IMPORTING iv_country TYPE land1
      RETURNING VALUE(rv_file) TYPE string.

  PRIVATE SECTION.
    CONSTANTS: c_chunk_size TYPE i VALUE 1000.

    DATA: mt_all_data  TYPE ty_customer_tab,
          mv_completed TYPE i,
          mv_total     TYPE i.
ENDCLASS.

CLASS zcl_mass_export IMPLEMENTATION.
  METHOD export_customers_parallel.
    " Load customer numbers
    SELECT kunnr FROM kna1
      WHERE land1 = @iv_country
      INTO TABLE @DATA(lt_customers).

    mv_total = lines( lt_customers ) / c_chunk_size + 1.
    mv_completed = 0.
    CLEAR mt_all_data.

    " Load chunks in parallel
    DATA: lv_from TYPE i VALUE 1,
          lv_chunk_no TYPE i VALUE 0.

    WHILE lv_from <= lines( lt_customers ).
      lv_chunk_no = lv_chunk_no + 1.

      " Calculate chunk range
      DATA(lv_to) = lv_from + c_chunk_size - 1.
      IF lv_to > lines( lt_customers ).
        lv_to = lines( lt_customers ).
      ENDIF.

      " Customer numbers for chunk
      DATA(lt_chunk_keys) = VALUE ty_kunnr_tab(
        FOR i = lv_from WHILE i <= lv_to
        ( lt_customers[ i ]-kunnr )
      ).

      " Load in parallel
      CALL FUNCTION 'Z_LOAD_CUSTOMER_DATA' STARTING NEW TASK |EXP{ lv_chunk_no }|
        DESTINATION 'NONE'
        CALLING on_chunk_loaded ON END OF TASK
        EXPORTING
          it_customers = lt_chunk_keys.

      lv_from = lv_to + 1.
    ENDWHILE.

    " Wait
    WAIT UNTIL mv_completed >= mv_total UP TO 600 SECONDS.

    " Write file
    rv_file = |/tmp/customers_{ iv_country }_{ sy-datum }.csv|.

    OPEN DATASET rv_file FOR OUTPUT IN TEXT MODE ENCODING UTF-8.
    IF sy-subrc = 0.
      TRANSFER 'KUNNR;NAME1;ORT01;LAND1' TO rv_file.
      LOOP AT mt_all_data INTO DATA(ls_data).
        DATA(lv_line) = |{ ls_data-kunnr };{ ls_data-name1 };{ ls_data-ort01 };{ ls_data-land1 }|.
        TRANSFER lv_line TO rv_file.
      ENDLOOP.
      CLOSE DATASET rv_file.
    ENDIF.
  ENDMETHOD.
ENDCLASS.

Destination Options

Destination	Description
`'NONE'`	Local server, same instance
`IN GROUP`	Use server group
`IN GROUP DEFAULT`	Default group
RFC destination	External system

WAIT Variants

" Wait for condition
WAIT UNTIL gv_done = abap_true.

" With timeout
WAIT UNTIL gv_done = abap_true UP TO 60 SECONDS.

" Wait for any task
WAIT FOR ASYNCHRONOUS TASKS UNTIL gv_count > 0.

" Multiple conditions
WAIT UNTIL gv_task1_done = abap_true
       AND gv_task2_done = abap_true
  UP TO 120 SECONDS.

Best Practices

Number of parallel tasks should match available work processes.
Use SPBT_INITIALIZE for server group configuration.
Error handling in RECEIVE RESULTS with EXCEPTIONS.
Always define timeout (UP TO … SECONDS).
No DB locks across tasks – avoid deadlocks.
Callback form/method must exist at runtime.
Optimize data volume per task (not too large, not too small).
RFC function modules must be remote-enabled.
COMMIT WORK only after all tasks complete.
Combine with HTTP Client for parallel API calls.