US Patent 8396831 Optimistic serializable snapshot isolation

The subject disclosure relates to a concurrency control technique that ensures isolation among concurrently execution transactions optimistically in a multiversion database by applying two optional tests at the end of a read-write transaction: validating the visibility of the read set of the read-write transaction(s) and phantom detection by re-scanning and confirming no new version have appeared in the view. Depending on desired level of isolation, both, one or none of the test are applied. Each version of a data record in an applicable database can be assigned two timestamps indicating the lifetime the version. The value of a version timestamp, though assigned, may be conditional on a transaction committing.