On concurrency control in multidatabase systems

A multidatabase system is a system that supports data access to a collection of preexisting autonomous database systems. Concurrency control in such an environment is much more diicult in nature than that in centralized or distributed (homogeneous) database systems. Many factors, especially the autonomies, bring diiculties to it. In this paper, we classify the multidatabase environment into value independent and value dependent ones, and discuss concurrency control mechanisms in these environments. We show that in the value independent environment, the task of concurrency control is resolvable by utilizing conventional concurrency control schemes. As for value dependent environment, we propose a general protocol which is deadlock free and preserves the local autonomy to solve the problems.