MULTICLASS TRANSACTION SCHEDULING AND OVERLOAD MANAGEMENT IN FIRM REAL-TIME DATABASE-SYSTEMS

Real-Time Database Systems (RTDBSs), have attracted considerable amoun t of research attention in the recent past and a number of important a pplications have been identified for such systems, such as telecommuni cations network management, automated air traffic control, automated f inancial trading, process control and military command and control sys tems. Due to the rapidity of change of the system state in such applic ations, as well as the inherent complexities in controlling such syste ms (which result in frequent violation of consistency requirements and consequent repeated firings of control actions), it is likely that th e transaction load in these systems would be fairly high. Thus RTDBSs need to be equipped with overload management mechanisms. Unfortunately overload management has been a fairly neglected area in real-time sys tems research in general and real-time database research in particular . In this paper we introduce Adaptive Access Parameter (AAP), a schedu ling mechanism for multiclass transactions in real-time database syste ms that employs an explicit admission control policy to manage overloa d as well as system bias towards particular transaction classes. We sh ow the theoretical underpinnings behind AAP and then report a thorough performance study that demonstrates AAP's substantial superiority ove r current algorithms with regard to performance metrics as well as com putational overhead.