PREEMPTIVE TRANSACTION SCHEDULING IN HARD REAL-TIME DATABASE-SYSTEMS

Hard real-time database systems (RTDBS) must provide a guarantee of me eting deadlines of transactions. Concurrent transaction accesses to sh ared data need to be synchronized in a serializable manner to ensure d atabase consistency. Transaction blocking is needed to resolve data co nflicts among transactions. This transaction blocking can be unbounded . Thus, transaction scheduling protocols for hard RTDBS must control a tight bound on the duration of a transaction blocking. In this paper, we present a new scheduling protocol that utilizes the operation sema ntics of transactions under the update-in-workspace model to enhance t ransaction preemptability, This protocol can alleviate the unnecessary transaction blocking problem associated with some other protocols. We show that this protocol has two important properties: single-blocking and deadlock-free. We devise a schedulability analysis which provides a better schedulability condition for systems using this protocol.