I was really shocked when I learned that EMC Documentum (Content Management solution) does not allow you to put itself into "online backup mode".
As we used Documentum with an Oracle database, and your content storage and DB should be backed up at the same time to ensure the consistency.
But the problem of implementaion of "hot backup" is obvious: we have to freeze the DB with metadata prior to backup of the filesystem. So what is the solution?
The key is here: perform regular Oracle hot backup and start fs backup from a notification script. This can lead to discrepancies between your content storage and metadata, but your Documentum admin will be able to delete all unnecessary files which were appeared after the DB backup.