How to get database size in DB6 using ABAP

After long research of searching function modules,... here is the example: 

  DATA lt_db6 TYPE STANDARD TABLE OF db6pmdb02.
  FIELD-SYMBOLS:
      <ls_db6> LIKE LINE OF lt_db6.
 
  CALL FUNCTION 'DB6_HIS_OVERVIEW'
*   EXPORTING
*     CONNECTION                  =
    TABLES
      it_db6pmdb02                = lt_db6
   EXCEPTIONS
     no_history_found            = 1
     invalid_parameter_set       = 2
     adbc_error                  = 3
     system_error                = 4
     OTHERS                      = 5.
 
  READ TABLE lt_db6 ASSIGNING <ls_db6> INDEX 1.
  IF <ls_db6> IS ASSIGNED.
    cv_size = <ls_db6>-totalkb.
    cv_size = cv_size / 1024.                               "2 get MB
  ENDIF.