HYBRID ATOMICITY FOR NESTED TRANSACTIONS

This paper defines the notion of hybrid atomicity for nested transacti on systems, and presents and verifies an algorithm providing this prop erty. Hybrid atomicity is a modular property; it allows the correctnes s of a system to be deduced from the fact that each object is implemen ted to have the property. It allows more concurrency than dynamic atom icity, by assigning timestamps to transactions at commit. The Avalon s ystem provides exactly this facility. The results in this paper extend earlier work using the same model for locking and timestamp-based alg orithms, providing further evidence for the generality of the approach . However, there are some subtle differences with the definitions used in earlier work, showing the difficulties of developing precise gener al models for nested transaction systems.