DATA gv_random(6) TYPE c. "Lenght = 6

CALL FUNCTION 'ISB_RANDOM_CHAR'
  EXPORTING
    length        = 6 " 6 chars...
    pattern       = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789'
  IMPORTING
    ran_char      = gv_random
  EXCEPTIONS
    invalid_input = 1
    OTHERS        = 2.
IF sy-subrc <> 0.
* Implement suitable error handling here
ENDIF.

WRITE gv_random.