??? All filegroups in the source database must be read/write and uncompressed: Snapshots
and compression don??™t mix, and it??™s necessary to write to filegroups in order
to restore them to their previous state.
??? All filegroups that were online when the snapshot was created must be online when
the snapshot is applied: This is because those filegroups must be written to in
order to restore them to their original state (i.e., to their state when the snapshot
was taken).
Reverting to a snapshot also breaks the transaction log chain. It rebuilds it during
the revert action, but be sure to back up the existing transaction log before applying the
snapshot; you may need it if a more drastic restore operation is required.
nNote It is extremely important to back up the tail of the transaction log before applying a snapshot.
Without that tail-log, you will lose data if you need to restore the database using a full backup that precedes
the snapshot. With normal restore operations, SQL Server 2005 prompts you to back up the tail-log
first??”it doesn??™t do so with snapshots. This is critical, because the instant the snapshot is applied, the
transaction log is reset, and those ???tail??? transactions are inaccessible.
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