SAP中如何查看BOM的修改记录呢？

concatenate sy-mandt 'M' itab_bom-stlnr into objectid.
  clear itab_cdhdr.
  refresh itab_cdhdr.
  clear change_data.
  refresh change_data.

  CALL FUNCTION 'CHANGEDOCUMENT_READ_HEADERS'
      EXPORTING
        DATE_OF_CHANGE    = '00000000'
        OBJECTCLASS       = 'STUE'
        OBJECTID          = objectid
        TIME_OF_CHANGE    = '000000'
        USERNAME          = ''
      TABLES
        I_CDHDR           = ICDHDR
      EXCEPTIONS
        NO_POSITION_FOUND = 1
        OTHERS            = 2.

  if icdhdr[] is not initial.
    loop at icdhdr where udate >= s_erdat-low.
      itab_cdhdr-objectclas = icdhdr-objectclas.
      itab_cdhdr-objectid = icdhdr-objectid.
      itab_cdhdr-changenr = icdhdr-changenr.
      itab_cdhdr-udate = icdhdr-udate.
      append itab_cdhdr.

      CALL FUNCTION 'CHANGEDOCUMENT_READ_POSITIONS'
        EXPORTING
          CHANGENUMBER      = ICDHDR-CHANGENR
*          TABLEKEY          = TABKEY
          TABLENAME         = 'STPO'
        IMPORTING
          HEADER            = CDHDR
        TABLES
          EDITPOS           = ICDSHW
       EXCEPTIONS
         NO_POSITION_FOUND = 1
         OTHERS            = 2.
*
*    select objectclas objectid changenr tabname tabkey fname chngind
*           value_new value_old from cdpos into table change_data
*     where objectclas = 'STUE' and objectid = bom_temp-objectid
*       and tabkey = bom_temp-tabkey and tabname = 'STPO' and
*           ( fname = 'IDNRK' or fname = 'MENGE' or fname = 'KEY' ).

     if icdshw[] is not initial.
       loop at icdshw.
         MOVE itab_cdhdr-objectclas  TO change_data-objectclas.
         MOVE itab_cdhdr-objectid  TO change_data-objectid.
         MOVE itab_cdhdr-changenr  TO change_data-changenr.
         MOVE itab_cdhdr-udate TO change_data-udate.
         MOVE ICDSHW-TABNAME TO change_data-tabname.
         MOVE ICDSHW-TABKEY TO change_data-tabkey.
         MOVE ICDSHW-FNAME TO change_data-fname.
         MOVE ICDSHW-F_OLD TO change_data-value_old.
         MOVE ICDSHW-F_NEW TO change_data-value_new.
         MOVE ICDSHW-CHNGIND TO change_data-chngind.
         APPEND change_data.
       endloop.
     endif.
    endloop.
  endif.