Kalen Delaney

Kalen Delaney has been working with SQL Server since 1987, and provides advanced SQL Server training to clients worldwide. She has been a SQL Server MVP since 1993 and has been writing about SQL Server almost as long. Kalen has spoken at dozens of technical conferences, including almost every PASS conference in the US since the organization’s founding in 1999. Kalen is the author or co-author of many books on SQL Server, including SQL Server 2012 Internals, from Microsoft Press. She is one of the main editors for SQL Server Central’s SQL Server Stairways Series. Kalen blogs at www.sqlblog.com and her personal website and schedule can be found at www.SQLServerInternals.com.
05 June 2014
05 June 2014

Row Versioning Concurrency in SQL Server

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The optimistic concurrency model assumes that several concurrent transactions can usually complete without interfering with each other, and therefore do not require draconian locking on the resources they access. SQL Server 2005, and later, implements a form of this model called row versioning concurrency. It works by remembering the value of the data at the start of the transaction and checking that no other transaction has modified it before committing. If this optimism is justified for the pattern of activity within a database, it can improve performance by greatly reducing blocking. Kalen Delaney explains how it works in SQL Server. … Read more
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