SELECT parameter||'='||VALUE "DBCharSet" 
  FROM nls_database_parameters 
 WHERE parameter = 'NLS_CHARACTERSET'

DROP TABLE utf8_4char_nodata

CREATE TABLE utf8_4char_nodata (title VARCHAR2(700))

DECLARE 
  t VARCHAR2(700); 
  v VARCHAR2(700); 
  d VARCHAR2(700); 
  c CLOB; 
BEGIN 
  INSERT INTO utf8_4char_nodata (title) VALUES (utl_raw.cast_to_varchar2('f0a1918d')); 
  COMMIT; 
 
  SELECT title, DUMP(title,16) 
    INTO t, d 
    FROM utf8_4char_nodata; 
 
  dbms_output.put_line(''); 
  dbms_output.put_line(d); 
  dbms_lob.createtemporary(c, TRUE); 
  FOR i IN 1..LENGTH(t) 
  LOOP 
    BEGIN 
      v := SUBSTR(t, i, 1); 
      dbms_output.put_line(v); 
      dbms_output.put_line('LENGTH() '||LENGTH(v)||' LENGTHB() '||LENGTHB(v)||' - '||TO_CHAR(ASCII(v), 'xxxxxxxxxx')); 
      dbms_lob.trim(c, 0); 
      dbms_lob.writeappend(c, length(v), v); 
      v := dbms_lob.substr(c); 
      dbms_output.put_line('LOB LENGTH() '||dbms_lob.getlength(c)||' - "'||v||'; '||TO_CHAR(ASCII(v), 'xxxxxxxxxx')||'"'); 
    EXCEPTION 
      WHEN OTHERS THEN 
        dbms_output.put_line(dbms_utility.format_error_stack); 
    END; 
  END LOOP; 
END;