Please help… with DDS5 backup tape..

Please help… with DDS5 backup tape..
i want to backup file or append file to tape using tar command but when i run the script there’s nothing error. But when I tar (-t) there’s no files have been append. The question is..
can’t DDS5 using tar -r command? any advices?? please answer ASAP.. please… very please..

thanks
luchan