Lazy consistency using loosely synchronized clocks

This paper describes a new scheme for guaranteeing that transactions in a clientlserver system observe consistent state while they are running. Thescheme ispresented inconjunction with at'toptimistic concurrency control algorithm, but could also be used to prevent read-only transactions from conflicting with read/write transactions in a multi-version system. The scheme is lazy about the consistency it provides forruming transactions and also in the way it generates theconsistency information. Thepaper presents results of simulation experiments showing that the cost of the scheme is negligible.