This option controls whether snapshot isolation is enabled for the database. Once this option is set to On, the database server
starts recording the original versions of updated rows in the temporary file if a transaction uses snapshot isolation.
If there are transactions in progress when the setting of the allow_snapshot_isolation option is changed, then the change
does not take effect immediately. Any transactions that are running when the option setting is changed from Off to On must
complete before snapshots can be used. When the setting of the option is changed from On to Off, any outstanding snapshots
are allowed to complete before the database server stops collecting version information, and new snapshots are not initiated.
You can view the current snapshot isolation setting for a database by querying the value of the SnapshotIsolationState database
SELECT DB_PROPERTY ( 'SnapshotIsolationState' );
The SnapshotIsolationState property has one of the following values:
Snapshot isolation is enabled for the database.
Snapshot isolation is disabled for the database.
Snapshot isolation is enabled once the current transactions complete.
Snapshot isolation is disabled once the current transactions complete.