Resolving Data Conflicts with Multiple Versions and Precedence Relationships in Real-Time Databases

We propose a multiversion concurrency control algorithm for real-time databases. Based on a priority cognitive algorithm commonly used in real-time processing, the proposed algorithm resolves data connicts among transactions in favor of the urgent transactions, i.e., those with higher priority. Our algorithm increases the degree of transaction concurrency while minimizing the transactions that miss their deadlines. This is achieved by using precedence relationships and multiple versions. A precedence relationship , which implies a serialization order among connicting transactions , is utilized to resolve data connicts and avoid deadlocks. The algorithm dynamically determines the abort of lower priority transactions depending on the likelihood of roll-backs and their states of execution. This leads to saving system resources by reducing unnecessary aborts of the lower priority transactions. We present some experimental results of our algorithm, comparing other real-time concurrency control algorithms. It is brieey shown that the proposed algorithm has superior performance to serveral algorithms for real-time databases.