一种面向混合实时事务调度的并发控制协议

首先给出了一个两层结构的混合实时数据库系统模型，其中支持采用非定期任务调度算法来改进系统的性能．进一步，针对这种模型下混合事务的数据一致性问题，提出了一种新的并发控制协议——MCC-DATI．该协议采用动态优先级驱动的调度算法，通过限制非定期的软实时事务对硬实时事务的阻塞时间，保证硬实时事务的可调度性；同时，采用非定期任务调度算法以及基于时间戳间隔的动态串行化顺序调整机制来减少软实时事务的截止期错失率．仿真实验表明，相对于先前的混合事务的并发控制协议，该协议在不同的系统负载与截止期约束下都能够改进系统的性能。

A Concurrency Control Protocol for Scheduling Mixed Real-Time Transactions

Previous study of real-time databases mainly focuses on scheduling and concurrency control of single type real-time transactions. However, there is a very common demand on processing mixed transactions. This paper first introduces a two-level real-time database system model, which provides the support of using aperiodic task scheduling algorithms to improve the system performance. Next, a new realtime concurrency control protocol called mixed concurrency control with dynamic adjustment of serialization order using timestamp intervals (MCC-DATI) is proposed to ensure the .data consistency among mixed transactions. The schedulability of hard real-time transactions can be guaranteed by adopting dynamic priority driven scheduling algorithm and bounding the blocking time from aperiodic soft real-time transactions, and the deadline miss ratio of soft real-time transactions may be reduced by adopting aperiodic task scheduling algorithm and dynamic adjustment of serialization order using timestamp intervals. Simulation experiments show that the MCC-DATI protocol can improve the system performance under different workloads and deadline constraints, as compared with previous concurrency control protocols of mixed transactions.