并行实时数据库系统中的一种自适应并发控制模式

根据事务的实时性及关键性分类，事务分为硬实时、固实时、软实时和非实时事务。传统的并发控制仅考虑其中一到两种事务，且将固／软实时事务统一为软实时事务考虑，带有很大的不精确性，这将降低系统吞吐率。为此，本文提出了一种自适应并发控制模式。该模式采用两级并发控制体系，一级是主并发控制器，探测不同类事务间可能存在
在的类间数据冲突；二级是从并发控制器，探测同类事务间可能存在的类内数据冲突，由四类从并发控制器实现。根据各类事务的不同特征，各控制器采用的策略不同，因而具有极大的自适应性并能最终提高系统的吞吐率，但需要增加额外的硬件开销。

An Adaptive Concurrency Control Mode in Parallel and Real-Time Database Systems

According to the real-time characteristics and criticality of transaction,it is classified as hard real-time transaction,firm real-time transaction,soft real-time transaction and non-real-time transaction.The traditional concurrency control strategy only considers one or two kinds of transactions,and considers the firm/soft real-time transaction as a unique soft real-time transaction,which features non-precision badly and then decreases system throughout. So,this paper brings forward an adaptive concurrency control mode for mixed transactions.The mode adopts a two-level concurrency control architecture,one level is a primary concurrency controller which detects probably existing data conflicts among different kinds of transactions;another is a subordinate concurrency controller which explores probably existing data conflicts amongst the same kind of transactions and serves as four subordinate concurrency controllers.Every controller uses a different control strategy due to the different properties of every transaction,so as to be provided with maximum adaptability and to enhance the system throughout ultimately,but it needs extra hardware overhead.