Oracle SQL function: CONVERT

declare
    nls_charset  varchar2(20);
    nls_charsetn varchar2(20);
    
    text_from     varchar2(30) := 'René';
    text_to      nvarchar2(30);
begin
   select value into nls_charset  from nls_database_parameters where parameter = 'NLS_CHARACTERSET'      ;
   select value into nls_charsetn from nls_database_parameters where parameter = 'NLS_NCHAR_CHARACTERSET';

   dbms_output.put_line('Converting from ' || nls_charset || ' to ' || nls_charsetn);
   text_to := convert(text_from, nls_charsetn, nls_charset);
   
   for r in (select
      dump(text_from, 16, 1, lengthb(text_from)) a,
      dump(text_to  , 16, 1, lengthb(text_to  )) b
   from
      dual
   ) loop
      dbms_output.put_line(r.a);
      dbms_output.put_line(r.b);
   end loop;
end;
/