The Freeze algorithms for concurrency control in secure real-time database systems

摘要

Database systems for real-time applications must satisfy timing constraints associated with transactions. Typically, a timing constraint is expressed in the form of a deadline and is represented as a priority to be used by schedulers. Recently, security has become another important issue in many real-time applications. In many systems, sensitive information is shared by multiple users with different levels of security clearance. As more advanced database systems are being used in applications that need to support timeliness while managing sensitive information, there is an urgent need to develop concurrency control (CC) algorithms in transaction management that satisfy both timing and security requirements. In this paper, we propose two CC algorithms that ensure both security and real-time requirements. The proposed algorithms are primarily based on MV locking. However, in order to satisfy timing constraints and security requirements, a new method, called the Freeze, is proposed. In addition, we show that our algorithms work correctly and they provide a higher degree of concurrency than existing MV algorithms. We present several examples to illustrate the behavior of our algorithms, along with performance comparisons with other algorithms. The simulation results show significant performance improvement of the proposed algorithms