Resumen de Speculative two-phase locking algorithm for distributed database systems
August Climent i Ferrer, Miquel Bertrán i Salvans, Miquel Nicolau Vila, Francesc Xavier Babot Pagès
This paper presents a new concurrency control algorithm for parallel database systems with a shared-nothing architecture. The algorithm which is used in these systems is strict two phase locking s-2pl. The new algorithm, speculative two-phase locking sp-2pl, is an extension of s-2pl. Other concurrency control algorithms outperform s-2pl under certain system conditions, but in general s-2pl gives better results. Our proposal, sp-2pl, allows to advance some operations but always giving a serializable schedule. The compatibility lock modes of operatons have been extended, and so the system can advance some operations in a speculative behavior. This situation is very useful in parallel database systems because the network overhead of our proposal has minimum impact on a system based on a fast interconnection network or on a bus. Our performance studies also show that the sp-2pl gives a better behavioral patten than the s-2pl, maintaining the robustness of s-2pl
