SQL Server 2005 Enterprise Edition and above supports the creation of database snapshots. These database snapshots are read-only views of a database at a certain point in time. Database snapshots are useful for troubleshooting database issues, as well as being very useful for generating reports when the reporting requires that the data in the database does not change while the reports are being generated. As such, snapshots are useful in circumstances such as billing cycles and end of year accounting.
Related to snapshot software is SQL comparision software such as SQL Compare. SQL comparison software is used to compare the differences between two databases, so is an essential tool where databases exist as both test, development and live databases.