Troubleshooting Row-Versioning–Based Snapshot-Based Isolation Levels

SQL Server 2005’s snapshot isolation levels are new features of the database engine that are specifically meant to improve concurrency. These two levels are:

  • READ COMMITTED SNAPSHOT: a variation of the default READ COMMITTED isolation level

  • SNAPSHOT ISOLATION: a new isolation level for explicit transactions. (We’ll refer to this option as Full SNAPSHOT to distinguish it more clearly from READ COMMITTED SNAPSHOT.)

We refer to these two options together as the snapshot-based isolation levels. A SELECT statement executing in a database with READ COMMITTED SNAPSHOT enabled will return committed data that is consistent as of the beginning of the SELECT statement. A SELECT statement ...

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