change default value from function

how to fix return value length on function level. Raw default value which returns is 2000, but I want to return 32000 bytes through function.

create or replace function hhh
return raw
is
begin
r raw(32000);

...
...
...

return r;
end;
/

here I get the error is raw returns more than 2000 bytes, but it can accept in r.

oracle ver : 9.2.0.8 Received on Tue May 22 2007 - 01:04:10 CDT