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

A distributed real-time active database system (DRTADBS) reacts to the critical events that occurred in the external environment by triggering of transactions. In this paper, the priority and deadline assignment to triggered transactions under two coupling modes, the deferred and immediate, in a DRTADBS is discussed. Two new approaches, the data state dependent (DSD) and the 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 de®ned according to the state 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 performance of these two approaches under the two coupling modes has been investigated. The results show that the DSD approach is more e€ective under the immediate coupling mode than under the deferred coupling mode due to the late creation of the triggered transactions under the deferred coupling mode. The TDD approach can improve the system performance under both deferred and immediate coupling mode. Ó 2000 Elsevier Science Inc. All rights