That being said, there are two areas to consider. If you perform a cold backup, you must have downtime for your database. If you cannot afford the downtime, then a cold backup is not for you. If you want or need to perform a hot backup, then you must be running in archive log mode.
Cold backups are easy, do not require archived redo logs, but require downtime. Hot backups do not require any downtime, but are a little more complex and require archived redo logs.
This was first published in June 2004