File Restore and Database Startup
This topic is relevant only for SQL Server databases that have multiple filegroups.
When a database is started, only filegroups whose files were online when the database was closed are recovered and brought online.
If a problem is encountered during database startup, recovery fails, and the database is marked as SUSPECT. If the problem can be isolated to a file or files, the database administrator can take the files offline and try to restart the database. To take a file offline, you can use the following ALTER DATABASE statement:
ALTER DATABASE database_name MODIFY FILE (NAME ='filename', OFFLINE)
If startup succeeds, any filegroup that contains an offline file remains offline.