how to call BAPI_ALM_ORDER_MAINTAIN

METHOD Ref : LIBAPI_ALM_ORDER_PROCESSINGCON

  DATA : lv_lines  TYPE i,
         lv_count  TYPE i,
         lv_last   TYPE c.

  DATA : lt_method TYPE TABLE OF bapi_alm_order_method
                        WITH HEADER LINE,
         lt_header TYPE TABLE OF bapi_alm_order_headers_i
                        WITH HEADER LINE,
         lt_headerx TYPE TABLE OF bapi_alm_order_headers_up
                        WITH HEADER LINE,

         lt_return TYPE TABLE OF bapiret2 WITH HEADER LINE.

  DESCRIBE TABLE gt_indexes LINES lv_lines.

  LOOP AT gt_indexes.

    CLEAR : lv_last.
    IF lv_lines EQ sy-tabix.
      lv_last = 'X'.
    ENDIF.

    READ TABLE gt_alv_dt INDEX gt_indexes-index.
    CHECK sy-subrc IS INITIAL.

    lv_count = lv_count + 1.
    lt_method-refnumber  = lv_count.
    lt_method-objecttype = 'HEADER'.
    lt_method-objectkey  = gt_alv_dt-aufnr.
    lt_method-method     = 'CHANGE'.
    APPEND lt_method.

    lt_method-objecttype = ' '.
    CASE lv_last.
      WHEN 'X'.
        lt_method-method     = 'SAVE'.
      WHEN space.
        lt_method-method     = 'DIALOG'.
    ENDCASE.
    APPEND lt_method.

    lt_header-orderid    = gt_alv_dt-aufnr.
    lt_header-systcond   = 1.
    APPEND lt_header.

    lt_headerx-orderid   = gt_alv_dt-aufnr.
    lt_headerx-systcond  = 'X'.
    APPEND lt_headerx.
  ENDLOOP.

  CALL FUNCTION 'BAPI_ALM_ORDER_MAINTAIN'
    TABLES
      it_methods   = lt_method[]
      it_header    = lt_header[]
      it_header_up = lt_headerx[]
      return       = lt_return.

  READ TABLE lt_return WITH KEY type = 'S'.
  IF sy-subrc IS INITIAL.
    CALL FUNCTION 'BAPI_TRANSACTION_COMMIT'
      EXPORTING
        wait = 'X'.
  ELSE.
    CALL FUNCTION 'BAPI_TRANSACTION_ROLLBACK'.
    DESCRIBE TABLE lt_return LINES lv_lines.
    READ TABLE lt_return INDEX lv_lines.
    PERFORM show_bapi_message USING lt_return.
  ENDIF.