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Brian Swan's Blog: SQL Server Driver for PHP Connection Options: Snapshot Isolation

Note: This article was originally published at PHPDeveloper on 16 September 2010.

Following up on his previous post about transaction-level isolation with the SQL Server driver, Brian Swan has this new look at an additional option - snapshot isolation.

I'll cover the snapshot isolation level in this post, and (as in my earlier post) I'll look at what happens at the database level when using a particular isolation level (rather than concentrating on PHP data access code).

He introduces snapshots for those not familiar with them - the idea of making a set of data available to other users without having to lock the database in a certain state (also called row versioning). He shows how to turn on the isolation functionality and set it to work with a transaction. With the snapshot created, he shows the SQL needed to fetch the snapshot of data and, of course, how to read it in PHP with the help of the SQL Server driver.