SCSA10-1 Objective 6.3 - Backup a mounted Solaris filesystem creating and backing up a UFS snapshot
Traditional UFS backup tools (like ufsdump) cannot do their job effectively with a busy, mounted, multiuser filesystem. The fssnap utility provides the capability to create a temporary copy (UFS snapshot) of an active, mounted filesystem which can then be backed up using ufsdump or other tools.
Backup a mounted file system by creating a UFS snapshot and performing a backup of the snapshot file.
Perusing the Internet, no one seems to have a better description of using fssnap to create UFS snapshots than Sun’s documentation page. This page also describes some things you can do with your snapshot once it is created, including backing it up using ufsdump.