Scheduling adaptive transactions in real-time databases

A new transaction model, called the Adaptive Transaction Model, is proposed for Real-Time Database Management Systems (RTDBMSs) applications. The Adaptive Transaction Model is an extended transaction model with a nested structure containing optional and required subtransactions. Adaptive Transactions (ATs) have time constraints to support real-time database applications. Optional substransactions can be omitted during the execution if time does not permit. Scheduling issues for a special case of adaptive transactions, called chain-structured adaptive transactions, are discussed. Several priority-based scheduling policies are proposed and experimental results are reported under lock-based and timestamp-ordering concurrency control protocols. A priority assignment policy (MSF-MES) is found to provide superior (low) miss ratios compared to other policies.