ON RIGOROUS TRANSACTION SCHEDULING

The concept of serializability is commonly used as a basic criterion for determining the correctness of concurrent execution of multiple transactions in database systems. Ensuring serializability is complicated, because transactions' serialization order does not need to correspond to their execution order. This anomaly is particularly troublesome in an environment consisting of multiple autonomous database systems in which global transactions are executed under the control of a multidatabase transaction scheduler, and local transactions are executed under the control of the local transaction scheduler. The above difficulties could be avoided if the serialization order of transactions (which is needed to determine the correctness of the schedules) was always the same as their execution and commitment order (which can be controlled by the scheduler). In this paper we define the class of transaction scheduling mechanisms in which the transaction serialization order can be determined by controlling their commitment order. This class of transaction management mechanisms is important, because it simplifies transaction management in a multidatabase system environment.