A Fair Locking Protocol for Multilevel Secure Databases

Most concurrency control algorithms for multilevel secure databases based on kernelized architecture prevent covert channels between transactions at different security levels by preempting the high security transaction in the event of a data conflict with a lower security transaction. In environments with moderate to high levels of contention between low and high security transactions, this can lead to poor performance and even starvation of high security transactions. In this paper, we examine this problem of unfairness in concurrency control mechanisms for secure databases. Based on an analysis of the performance of a secure version of twophase locking, we propose three different modifications to the protocol that address the problem of starvation of high security transactions. Through a detailed simulation study, we examine the fairness and performance of these approaches for a variety of workloads.