Preemptive transaction scheduling in hard real-time database systems

Hard real-time database systems (RTDBS) must provide a guarantee of meeting deadlines of transactions. Concurrent transaction accesses to shared data need to be synchronized in a serializable manner to ensure database consistency. Transaction blocking is needed to resolve data conflicts 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 semantics of transactions under the update-in-workspace model to enhance transaction 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.