Abstract
Most of the proposed concurrency control protocols for real-time database systems are based on serializability theorem. Owing to the unique characteristics of real-time database applications and the importance of satisfying the timing constraints of transactions, serializability is too strong as a correctness criterion and not suitable for real-time databases in most cases. On the other hand, relaxed serializability including epsilon-serializability and similarity-serializability can allow more real-time transactions to satisfy their timing constraints, but database consistency may be sacrificed to some extent. We thus propose the use of weak serializability(WSR) that is more relaxed than conflicting serializability while database consistency is maintained. In this paper, we first formally define the new notion of correctness called weak serializability. After the necessary and sufficient conditions for weak serializability are shown, corresponding concurrency control protocol WDHP(weak serializable distributed high priority protocol) is outlined for distributed real-time databases, where a new lock mode called mask lock mode is proposed for simplifying the condition of global consistency. Finally, through a series of simulation studies, it is shown that using the new concurrency control protocol the performance of distributed real-time databases can be greatly improved.
Similar content being viewed by others
References
Harista J R, Ramamritham K. Real-time databases in the new millennium [J]. Real-Time Systems, 2000,19(3): 205–215.
Bharat Bhargave. Concurrency control in database system [J]. IEEE Transactions on Knowledge and Data Engeering, 1999, 11(1): 3–16.
Wu K L, Yu P S, Pu C. Divergence control for epsilon-serializability [A]. In proceeding of 8th International Conference on Data Engineering [C]. Phoenix, February 1992: 128–138.
Kam Yiu Lam, Wai Cheng Yau. On using similarity for concurrency control in real-time database systems [J]. The journal of Systems and Software, 1998, 43 (3): 223–232.
Stankovic J A, Son S H, Hansson J. Misconceptions about real-time databases [J]. Computer, 1999, 32(6): 29–37.
Son S, Zhang F. Real-time replication control for distributed database systems: algorithms and their performance [A]. 8th International Conterence on Database Systems for Advanced Applications [C]. Singapore, April 1999: 50–59.
Lam K, Hung S L. Concurrency control for time-constrained transactions in distributed database systems [J]. The Computer Journal, 1995, 138(9): 704–715.
Author information
Authors and Affiliations
Additional information
Project supported by the National Natural Science Foundation of China (60073045) and the Commission of Science, Technology and Industry for National Defense of China (00J15. 3. 3. JW0529)
About this article
Cite this article
Dang, DP., Liu, YS. & Pan, L. Weak serializable concurrency control in distributed real-time database systems. J. of Shanghai Univ. 6, 325–330 (2002). https://doi.org/10.1007/s11741-002-0059-3
Received:
Revised:
Issue Date:
DOI: https://doi.org/10.1007/s11741-002-0059-3