Classes of Serializable Histories and Synchronization Algorithms in Distributed Database Systems

The classes of serializable histories for distributed database systems are studied. The study is based on the model of partially redundant distributed database and multiple read/write transactions. Classes are identified by timing constraints on the system history. Five classes (g2pl, l2pl, dcp, dsto, and dss) are described. A hierarchy among these classes has been established. Since most of the existing synchronization algorithms are for class g2pl or class dsto and the concurrency provided by these two classes is low, characteristics of new algorithms which can belong to other classes are investigated. Specifically, certain system characteristics which will allow the degree of concurrency to be increased are presented. 15 references.