Hi Mike ,
Before you can restore system databases from SnapManager backup sets:
1. The system databases must be migrated to LUNs.
2. SnapManager must be used to create stream-based backup sets of those databases.
The procedure to restore your SQL Server system database depends on whether the database is still functional. If the database is no longer functional, you must rebuild the system databases first.
Full database stream-based backup files are .fbk files .It is similar to .bak file in SQL Server.
Regards,
Abhishek