Detection of mutual inconsistency in distributed databases

Abstract

A Distributed Database Management System should guarantee the consistency of databases at all sites in the system. In particular when the databases are replicated, mutual consistency among all copies of an item should be maintained. Network partitioning is a difficult kind of failure to deal with. A strategy known as the optimistic approach allows transactions to be run independently in different parts of the distributed system formed due to a partition. The mutual consistency among the copies of an item cannot be taken for granted in this scenario. Thus a natural requirement of the system then is that it determines whether or not the database is consistent and tries to resolve any inconsistencies. A simple scheme is presented in this paper to detect mutual inconsistency when partitioned databases merge. This scheme is similar to that of D. S. Parker et al. [ IEEE Trans. Software Eng. (May 1983)] in spirit although it is more general. In contrast to that of S. Davidson [ ACM Trans. Database Systems (Sept. 1984), 456–482] where a certain amount of information is maintained about each transaction run after the partition, our scheme maintains certain information with each data item accessed after the partition.