Isolation and Lock Levels Supported

Microsoft SQL Server supports isolation levels 0 (Read Uncommitted), 1 (Read Committed), 2 (Repeatable Read), and 3 (Serializable). Microsoft SQL Server supports row-level and table-level locking. Refer to Chapter 7 “Locking and Isolation Levels” in the DataDirect Connect Series for ODBC Reference for details.

Microsoft SQL Server 2005 and higher supports the following additional isolation levels:

■

Snapshot

■	Read Committed with Snapshots

■	Read Committed with Locks (equivalent to Read Committed in previous Microsoft SQL Server versions)

Using The Snapshot Isolation Level

The Snapshot isolation level is available only with Microsoft SQL Server 2005 and higher. Setting the SnapshotSerializable connection string attribute changes the behavior of the Serializable isolation level to use the Snapshot Isolation level. This allows an application to use the Snapshot Isolation level with minimal or no code changes.

If you are writing a new application, you may want to code it to set the connection attribute SQL_COPT_SS_TXN_ISOLATION to the value SQL_TXN_SS_SNAPSHOT. The application then uses the snapshot isolation level without requiring the Use Snapshot Transactions connection option.

See “Use Snapshot Transactions” for additional information.