A new priority assignment algorithm called adaptive earliest deadline (AED) is given that stabilizes the overload performance of the earliest deadline policy in a real-time database system (RTDBS) environment. The AED algorithm uses a feedback control mechanism to achieve this objective and does not require knowledge of transaction characteristics. Using a detailed simulation model, the authors compare the performance of AED with respect to earliest deadline and other fixed priority schemes. They also present and evaluate an extension of the AED algorithm called hierarchical earliest deadline (HED), which is designed to handle applications that assign different values to transactions and where the goal is to maximize the total value of the in-time transactions.
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