Applying Method Data Dependence

Concurrency control in object based systems is a new area of research that has only just begun to be addressed. Recent work has proposed using object level locking but this may be unnecessarily restrictive. Data level locking within an object increases concurrency but also introduces substantial lock overhead that makes the approach impractical. This paper proposes using a new approach applying method level dependence analysis techniques to object bases using a nested transaction model. Three algorithms are proposed. The rst algorithm uses static analysis of methods invoked by user transactions only. The second performs runtime analysis of the nested methods invoked by the methods invoked by user transactions. Finally, a third algorithm proposes a hybrid technique that is compatible with both of these techniques and determines if the acquisition of locks is necessary at runtime or if the method can be invoked without the possibility of con ict. This algorithm is e cient, simple, and completely compatible with two{phase locking. The complexity of each algorithm and other areas of application of dependence analysis are also discussed. Applying Method Data Dependence to Transactions in Object Bases 1