The commit/abort problem in type-specific locking

Type-specific locking is designed to increase performance of distributed transactions by allowing competing transactions to concurrently alter shared objects concurrently, provided their changes are commutative. When one of the set of compatible transactions commits or aborts, a problem arises due to the indeterminacy of the alterations of the others. A tree of nineteen solutions to the problem has been investigated. Given the necessary support by the underlying architecture, this tree can be pruned severely. The problem and set of approaches came to the authors´ attention during design for type-specific locking in PROFEMO, an operating system for a local area network that provides a location-independent object environment and built-in mechanisms for transaction control and recovery. A description is given of the problem, the possible solutions, and the arguments that allow the pruning. Testbed results are not yet available, since type-specific locking has not yet been implemented at the time of the initial tests of the PROFEMO system