Locking in the Database Engine

For more information about the specific types of locking or row versioning controlled by each

transaction isolation level, see

SET TRANSACTION ISOLATION LEVEL (Transact-SQL).

Transaction isolation levels can be set using Transact-SQL or through a database API.

Transact-SQL scripts use the

statement.

ADO applications set the

property of the

object to

, or.

ADO.NET applications using the

managed

namespace can call the

method and set the

option to

or.

When starting a transaction, applications using OLE DB call

with

set to

, or.

When specifying the transaction isolation level in autocommit mode, OLE DB applications can set

the

property

, or.

ODBC applications call

with

set to

and

set to

, or.

For snapshot transactions, applications call

with Attribute set to

and

set to. A snapshot transaction can

be retrieved using either

or.

SET TRANSACTION ISOLATION LEVEL

IsolationLevel

Connection

adXactReadUncommitted

adXactReadCommitted

adXactRepeatableRead

adXactReadSerializable

Microsoft.Data.SqlClient

System.Data.SqlClient

SqlConnection.BeginTransaction

IsolationLevel

Unspecified

Chaos

ReadUncommitted

ReadCommitted

RepeatableRead

Serializable

Snapshot

ITransactionLocal::StartTransaction

isoLevel

ISOLATIONLEVEL_READUNCOMMITTED

ISOLATIONLEVEL_READCOMMITTED

ISOLATIONLEVEL_REPEATABLEREAD

ISOLATIONLEVEL_SNAPSHOT

ISOLATIONLEVEL_SERIALIZABLE

DBPROPSET_SESSION

DBPROP_SESS_AUTOCOMMITISOLEVELS

DBPROPVAL_TI_CHAOS

DBPROPVAL_TI_READUNCOMMITTED

DBPROPVAL_TI_BROWSE

DBPROPVAL_TI_CURSORSTABILITY

DBPROPVAL_TI_READCOMMITTED

DBPROPVAL_TI_REPEATABLEREAD

DBPROPVAL_TI_SERIALIZABLE

DBPROPVAL_TI_ISOLATED

DBPROPVAL_TI_SNAPSHOT

SQLSetConnectAttr

Attribute

SQL_ATTR_TXN_ISOLATION

ValuePtr

SQL_TXN_READ_UNCOMMITTED

SQL_TXN_READ_COMMITTED

SQL_TXN_REPEATABLE_READ

SQL_TXN_SERIALIZABLE

SQLSetConnectAttr

SQL_COPT_SS_TXN_ISOLATION

ValuePtr

SQL_TXN_SS_SNAPSHOT

SQL_COPT_SS_TXN_ISOLATION

SQL_ATTR_TXN_ISOLATION