At work (when I had a job) we had ScoUnix Servers running 8i using BackUPEdge backup software, and NT4 Servers running 8i and using Veritas Backup Exec. We did a hotbackup on the Unix servers every night. The Backup edge software would lock the database during backup preventing other clients from getting access. In the end we had to shutdown the database during hotbackup.

Hotbackup is good if you run a 24/7 operation and cant afford to take the database offline.

But its good to periodically take a cold backup.