Detection of mutual inconsistency in Distributed Databases

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. Concurrency control mechanisms achieve this when there are no failures, but they fail when failures occur. Network partitioning is a hard kind of failure to deal with and mutual consistency among copies of items cannot be taken for granted in presence of a partitioning. A simple scheme is presented in this paper to detect mutual inconsistency when partitioned databases merge. This scheme is similar to that of Parker et al [7] in spirit and is more general than theirs. In contrast to Davidson´s [3] where some amount of information is maintained about each transaction run after the partition, we maintain some information with each data item accessed after the partition.