In a real-time application, a transaction may be assigned a value to reflect the profit of completing the transaction before its deadline. Satisfying both goals of maximizing the totally obtained profit and minimizing the number of missed transactions at the same time is a challenge. The authors present an adaptive real-time scheduling policy named value-based processor allocation (VPA-k) for scheduling value-based transactions in a multiprocessor real-time database system. Using the VPA-k policy, the transactions with higher values are given higher priorities to execute first, while at most k percentage of total processors are dynamically allocated to execute the urgent transactions. Through simulation experiments, VPA-k is shown to outperform other scheduling policies substantially in both maximizing the totally obtained profit and minimizing the number of missed transactions under various system environments.
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