14 The SQL Server Legacy Wire Protocol Driver : Performance Considerations

Performance Considerations
Use Snapshot Transactions (SnapshotSerializable): You must have your Microsoft SQL Server 2005 and higher database configured for snapshot isolation for this connection option to work. Snapshot Isolation provides transaction-level read consistency and an optimistic approach to data modifications by not acquiring locks on data until data is to be modified. This Microsoft SQL Server 2005 and higher feature can be useful if you want to consistently return the same result set even if another transaction has changed the data and 1) your application executes many read operations or 2) your application has long running transactions that could potentially block users from reading data. This feature has the potential to eliminate data contention between read operations and update operations. When this connection option is enabled, performance is improved due to increased concurrency.
See “Using The Snapshot Isolation Level” for details.