On using similarity for concurrency control in real-time database systems

Most of the proposed concurrency control protocols for real-time database systems (RTDBS) are based on serializability theorem. Owing to the unique characteristics of real-time database applications and the importance of satisfying the timing constraint of the transactions, serializable concurrency control protocols are not suitable for RTDBS for most cases. In this paper, another notion of correctness, similarity, is used for concurrency control in a RTDBS, for instance, a stock trading database system. Similarity is a less restrictive notion comparing with serializability. By studying the correctness requirements of the stock trading database applications, a real-time two phase locking protocol, High Priority 2 Phase Locking (H2PL) is re-defined based on similarity. Although the new protocol cannot ensure serializability, the concurrency of the system is higher and the amount of inconsistency in the database is tolerable. On the other hand, the performance of the whole system can be much improved.

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