As of ARCserve 12.0 the default ARCserve database is SQL Express, however SQL Server can also be used. If the database resides on another system then during the installation of ARCserve just point it to the location of the database and select to not overwrite the database.
By detault ARCserve creates a database protection job to backup the SQL Express database. When SQL Server is used it is backed up via the SQL Client Agent.
Typically every backup tape will contain a session for the backup of the database. To located the session run a San on the tape and the Job Log will report the sessions on tape.
Once the session has been identified it is just a matter of restorying it. The Amin Guide has details on all of this.
Alternatively you can just Merge (Quick Start > Utilities > Merge) in any tape if a quick restore is needed.