Global predicate-based locks in long-running transactions

Previous work on long-running transactions for multi-database environments relaxes the isolation requirement of conventional ACID transactions. However, most of that work does not provide mechanisms to explicitly enforce isolation. This paper proposes a framework in which long-running transactions can specify global predicate-based locks to enforce limited forms of isolation between selected transactions. The framework appears to be especially useful in contexts where there is a class of transactions with stringent deadlines, and another class of transactions making multi-database updates that do not have stringent deadlines. This report motivates and presents the framework, and illustrates its use in connection with maintaining inter-database constraints.