Isolation Levels
The SQL Server driver supports the following isolation levels for Microsoft SQL Server:

Read Committed with Locks * or Read Committed

Read Committed with Snapshots *

Read Uncommitted

Repeatable Read

Serializable

Snapshot *
* Supported for Microsoft SQL Server 2005 and higher only.
The default is Read Committed with Locks (Microsoft SQL Server 2005 and higher) or Read Committed.