Oracle创建禁止DDL的触发器

create or replace trigger forbid_ddl
       before ddl on DATABASE
begin
  --if ora_dict_obj_owner = ora_login_user then
  --  return;
 -- end if;
  raise_application_error (-20000, '零一二三四五六七八九零一二三四五六七八九零一二三四五六七八九零一二三四五六七八九零一二三四五六七八九零一二三四五六七八九零一二三四五六七八九零一二三四五六七八九零一二三四五六七八九零一二三四五六七八九');
end;