Josep M. Bernabé-Gisbert et al.: Extending Mixed Serialisation Graphs to Replicated Environments TR-ITI-ITE-07/20 Extending Mixed Serialisation Graphs to Replicated Environments

Abstract

A Database Management System normally deals with a heterogeneous set of transactions which do not necessarily need the same isolation guarantees if executed concurrently. Centralised DBMSs can manage this kind of situations since they normally use locks and every transaction implicitly requests the necessary locks to ensure its isolation needs. Nevertheless, in replicated environments this issue is not solved since the most used replication schemes can not be easily adapted to such a heterogeneous environment as in centralised ones. In fact, it is even hard to prove whether a replication protocol is ensuring every transaction isolation guarantees unless only one isolation level at a time is supported. In this document we extend Adya’s Mixed Serialisation Graphs with more isolation levels and apply them to replicated environments to be able to know when a given replication protocol ensures every transaction guarantees.