To find the current version of SQL Server that you have installed, see How to determine the version, edition and update level of SQL Server and its components. In this scenario, the SELECT query that is trying to access SourceTable will be blocked. While one transaction is holding an exclusive lock on an object (for example, an ongoing table update), another transaction is executing parallelized SELECT (…) FROM SourceTable by using the NOLOCK hint. In this scenario, other queries that try to access SourceTable will be blocked. The patterns that are exposed to this blocking issue are as follows:Įxecuting a parallelized SELECT (…) INTO Table FROM SourceTable statement, and specifically using the NOLOCK hint, under the default SQL Server lock-based isolation level or higher. In this situation, you may encounter queries that experience blocking or deadlocks. 0, KB 3144524), and that you are running workload patterns that include parallel SELECT(…)WITH NOLOCK, under the default SQL Server lock-based isolation level or a higher level. NOLOCK (or SET TRANSACTION ISOLATION LEVEL READ UNCOMMITTED - whew) can certainly be useful in circumstances where you do not have deadlocks. A normal sql select query will wait for the transaction to complete, thus degrading the performance of the application or screen which is executing. Consider you are updating multiple records within a transaction.
#SQL DEADLOCK WITH NOLOCK INSTALL#
Assume that you install the original released and now deprecated Cumulative Update 6 for SQL Server 2014 Service Pack 1 (SP1) (build number. So let us see how NoLock hint increase the performance of the query.
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