RELATIVE SERIALIZABILITY - AN APPROACH FOR RELAXING THE ATOMICITY OF TRANSACTIONS

Serializability is too strong a correctness criterion and unnecessaril y restricts concurrency. We use the semantic information of a transact ion to provide different atomicity views of the transaction to other t ransactions. The proposed approach improves concurrency and allows int erleavings among transactions which are nonserializable, but which non etheless preserve the consistency of the database and are acceptable t o the users. We develop a graph-based tool whose acyclicity is both a necessary and sufficient condition for the correctness of an execution . Our theory encompasses earlier proposals that incorporate semantic i nformation of transactions. Furthermore, it is the first approach that provides an efficient graph-based tool for recognizing correct schedu les without imposing any restrictions on the application domain. Our a pproach is widely applicable to many advanced database applications su ch as systems with long-lived transactions and collaborative environme nts. (C) 1997 Academic Press.