Priority and deadline assignment to triggered transactions in distributed real-time active databases

A distributed real-time active database system (DRTADBS) reacts to the crit ical events that occurred in the external environment by triggering of tran sactions. In this paper, the priority and deadline assignment to triggered transactions under two coupling modes, the deferred and immediate, in a DRT ADBS is discussed. Two new approaches, the data state dependent (DSD) and t he transaction-data deadline (TDD), are proposed to assign criticality and deadlines to the triggered transactions, respectively. In the DSD approach, the criticality of a triggered transaction is defined according to the sta te of the temporal data object which is responsible for its triggering. The objective of the DSD approach is to increase the number of commit achieved by the triggered transactions especially the more critical ones. The perfo rmance of these two approaches under the two coupling modes has been invest igated. The results show that the DSD approach is more effective under the immediate coupling mode than under the deferred coupling mode due to the la te creation of the triggered transactions under the deferred coupling mode. The TDD approach can improve the system performance under both deferred an d immediate coupling mode, (C) 2000 Elsevier Science Inc. All rights reserv ed.