AN ANALYSIS OF LOCK-BASED AND OPTIMISTIC CONCURRENCY-CONTROL PROTOCOLS IN MULTIPROCESSOR REAL-TIME DATABASES

Previous studies, e.g., Haritsa et al. (Haritsa, J.R., Livny, M., Care y, M., 1990. Proceedings of Ninth ACM Symposium on Principles of Datab ase systems) have shown that optimistic concurrency control (OCC) gene rally performs better than lock-based protocols in disk-based real-tim e database systems (RTDBS). In this paper we compare the two concurren cy control protocols in both disk-based and memory-resident multiproce ssor RTDBS. Based on simulation, we analyze the intrinsic behaviors of the two protocols. The result of our performance evaluation experimen ts show that different characteristics of the two environments indeed have great impact on the protocols' performance. We identify such syst em characteristics and expose the weaknesses of traditional OCC and lo ck-based protocols. To improve performance, a new protocol, called Two Phase Locking-Lock Write All (2PL-LW), is proposed. We show that 2PL- LW performs better than the traditional protocols in meeting transacti on deadlines in both disk-based and memory-resident RTDBS. (C) 1998 El sevier Science Inc. All rights reserved.