read committed isolation level sql server 2012

Specifies that statements cannot read data that has been modified but not committed by other transactions. For more information about snapshot isolation, see Snapshot Isolation in SQL Server. The READ COMMITTED isolation level with the READ_COMMITTED_SNAPSHOT database option set to ON. In SQL Server, you can also minimize locking contention while protecting transactions from dirty reads of uncommitted data modifications using either: This is the least restrictive of the isolation levels. This option has the same effect as setting NOLOCK on all tables in all SELECT statements in a transaction. Values in the data can be changed and rows can appear or disappear in the data set before the end of the transaction. When this option is set, it is possible to read uncommitted modifications, which are called dirty reads. READ UNCOMMITTED transactions are also not blocked by exclusive locks that would prevent the current transaction from reading rows that have been modified but not committed by other transactions. Transactions running at the READ UNCOMMITTED level do not issue shared locks to prevent other transactions from modifying data read by the current transaction. Specifies that statements can read rows that have been modified by other transactions but not yet committed. To view Transact-SQL syntax for SQL Server 2014 and earlier, see Previous versions documentation.

Read committed isolation level sql server 2012