Every time a backup is taken, the current time forms its snapshot identifier.
Some additional information can be stored along with it in the table SnapshotStore.
The meta data about files in FileInformationStore and its blocks in FBlockListStore contain a reference to a snapshot. This introduces an additional dimension of time: we can distinguish when a block has been changed, or when file meta data has changed.
spTimestamp is the time when the backup began. It is the main reference to the snapshot.
spEndtime is the time when the backup finished. No file in the backup is younger than this time.
we can also record the hostname and the user who initiated the backup for loging purpose.