区分移动实时事务关键性的并发控制策略

在移动实时数据库系统中,事务的关键性代表实时事务的时间紧迫性,由于实时事务的紧迫程度不同,为了保证事务的时间正确性,因而有必要区分事务的关键性提出相应的并发控制策略。该文按满足截止时间的重要性将实时事务分为软、硬事务加以研究,在此基础上分别提出了三种区分事务关键性的优先级并发控制策略,对三种优先级策略进行了性能比较并提出了改进方法。研究结果表明,将实时事务按关键性分类有利于设计事务优先级分派及调度策略。     

数据库入侵检测的一种数据挖掘方法

针对在数据库系统中检测恶意事务提出了一种数据挖掘方法。该方法挖掘数据库中各数据项事务之间的数据关联规则,所设计的数据关联规则挖掘器主要用来挖掘与数据库日志记录相关的数据。不符合关联规则的事务作为恶意事务。试验证明该方法可以有效的检测到恶意事务。     

区分移动实时事务关键性的并发控制策略

在移动实时数据库系统中,事务的关键性代表实时事务的时间紧迫性,由于实时事务的紧迫程度不同,为了保证事务的时间正确性,因而有必要区分事务的关键性提出相应的并发控制策略。该文按满足截止时间的重要性将实时事务分为软、硬事务加以研究,在此基础上分别提出了三种区分事务关键性的优先级并发控制策略,对三种优先级策略进行了性能比较并提出了改进方法。研究结果表明,将实时事务按关键性分类有利于设计事务优先级分派及调度策略。     

相交数据集合的R／W事务可串行化判别方法

R/W事务是应用中广泛存在的一类人工交互性长事务,采用传统的两段锁协议对R/W事务进行并发控制,会严重影响到系统的执行效率.为此,曾经提出一种基于数据集合分析的新的并发控制方法.有效地解决了系统效率的问题.然而,以前的方法在相交数据集合的情况下,使用较为复杂.并且对于两种类型的R/W事务一原子关系和相交数据集合关系,事务提交采用了不同的判别准则;增加了系统实现的复杂度.本文在原有方法的基础上,通过对R/W事务特性的进一步分析和对数据集合关系的演绎推理,提出了新的事务提交判别准则,统一了两种类型R/W事务的并发控制策略.新的方法具有更高的效率,且简单易行,提高了系统的可实现性.     

组件的可靠事务设计一致性验证研究

在基于组件的系统开发中,组件的事务控制粒度从语句一级被提升到方法一级,因此给系统开发人员带来了便利性的同时,失去了对事务控制的灵活性,通过研究,提出了一种从组件的事务属性和隔离性两方面来判定组件事务设置是否正确的方法,便开发人员能设计出拥有可靠事务的组件应用系统。     

基于Annotation的Spring事务应用设计

讲解Spring的事务实现技术,讨论Spring中事务的两种实现方式。通过同一个案例阐述了在Spring中对XML配置来实现事务和使用了Annotation实现事务,比较了两种实现方式的优缺点。在Spring使用Annotation实现事务作出总结,从而体现使用Annotation实现事务简洁性和良好的扩展性。     

基于Apriori 分类事务库关联规则算法

Apriori 算法是通过定义的事务库来生成频繁项集,确定各数据之间的关联规则。在实际应用中生成事务库时常常会出现同一项目中重复类型的事务库,而同一项目的事务之间的支持度为零。因此,事务库的定义方法是直接影响生成关联规则的生成速度与效率,针对这一问题,本文提出并实现了一种基于Apriori 分类事务库的关联规则算法。该方法改变了传统Apriori 算法中所有事务统一定义的方法,对不同项目的事务进行分类定义,通过这种的实现,不但减少了计算机的大量运算,而且提高了关联规则的生成速度。     

分布式主动实时数据库基于多优先级队列的优先级分派

事务的分布性和事务触发的不可预测性使得分布式主动实时数据库系统中的事务调度变得较为复杂．该文给出了立即和推迟两种模式下执行的被触发事务的截止期确定方法和事务紧急度计算方法,并结合事务的应用语又提出了一种基于多优先级队列的优先级分派策略,有利于主动事务和被触发事务的顺利提交．     

软件事务内存的动态竞争管理策略

软件事务内存是为了简化并行程序设计而出现的一种新的程序设计技术.为了降低软件事务内存系统中事务冲突的发生频率以提升系统整体性能,提出了一种新的基于动态控制和队列调度的竞争管理策略.定义了竞争强度的概念和系统总体框架,并在此基础上给出了利用运行时反馈信息动态调节竞争强度的方法.同时给出了事务序列化的设计方法与实现中应注意的问题,通过将冲突概率大的事务序列化以达到避免相同冲突再次发生的目的.结合常用的基准数据结构,对模型和算法进行了实验,最后结果表明了算法的正确性和有效性.     

基于Annotation的Spring事务应用设计

该文简要介绍Spring的事务实现技术,讨论了Spring中的事务的两种实现方式。通过同一个案例阐述了在Spring中通过xml配置来实现事务和使用了Annotation实现事务,比较了两种实现方式的优缺点。对在Spring使用Annotation实现事务作了总结,从而体现使用Annotation实现事务简洁性和良好的扩展性。     

移动多数据库事务模型及其可串行化事务管理

提出了一个移动多数据库全局事务模型及其可串行化事务管理技术。该技术通过从各自治站点中获取本地可串行化信息构造全局事务可串行化图GTSG来判定全局事务的可串行性。它支持全局事务的迁移、网络的断接(包括可能发生的灾难性断接)并保证全局事务的关键站点子事务的原子性和隔离性。     

Revisiting Transaction Management in Multidatabase Systems

A lot of research efforts have focused on global serializability, global atomicity, and global deadlocks in multidatabase systems. Surprisingly, however, very few transaction processing model exists that ensures global serializability, global atomicity, and freedom from global deadlocks in a uniform manner. In this paper, we examine previous transaction processing models and propose a new transaction processing model that generates globally serializable and deadlock-free schedules in failure-prone multidatabase systems. A new transaction processing model adopts rigid conflict serializability as a correctness criterion on global serializability, and follows an emulated 2PC, criteria for global commitment, and an abort-based multidatabase recovery scheme for global serializability in failure-prone multidatabase systems. In addition, a deadlock-free policy is suggested where rigid conflict serializability is enforced when each subtransaction, including redo transactions, begins its execution. To practically support a new transaction processing model, Rigid Ticket Ordering (RTO) methods are designed. The proposed transaction processing model has the following improvements: (a) it resolves abnormal direct conflicts identified in this paper, (b) it imposes no restrictions on the execution of local transactions, and (c) it relaxes the restrictions on the execution of global transactions.     

多库系统的两阶段局部代理失败恢复策略

从保证全局事务的ACID性及实际的可操作性出发，提出了一种较为可靠的两阶段局部代理的工作流程，使用局部代理作为全局事务管理系统与局部数据库的中间层，模拟出符合2PC协议的状态，从而在多数据库的事务处理中使用2PC协议，在最大限度保证异构数据库自治的前提下，从一定程度上解决了全局事务的原子性保证问题和局部站点失败恢复的问题     

带有公平电子合同的交易协议

基于原子的公平匿名交易协议,采用两阶段提交的思想,通过可信第三方TTP(trusted third party)来控制交易的提交。在进行大量交易时,TTP会成为瓶颈。文中在原协议的基础上进行改进,引入了公平电子合同,改变交易提交方式,减少了TTP的工作量,但并没有破坏其原子性和公平匿名性,同时交易后产生的电子合同可具有传统交易合同的作用。     

多级安全数据库系统中多级事务原子性的研究

文章在证明了不可能同时保证多级事务的原子性和安全性的基础上,介绍了多级事务三种不同程度的原子性,给出了两种基本算法,并通过引入多版本机制消除事务节间的语义依赖。     

原子和公平匿名的电子交易协议的研究

基于公平盲签名技术、两阶段提交技术以及混合加密和数字签名技术,该文首次提出了一个能同时实现原子性和公平匿名性的电子交易协议。协议除了具有很好的原子性和匿名性外,对于非法的交易还提供了疑点追踪。文章详细描述了协议的工作过程,并分析了协议的原子性和匿名性。     

Global committability in multidatabase systems

Develops a formal basis for research into the reliability aspects of transaction processing in multidatabase systems (MDBSs). We define a new correctness notion called `global committability' for the correct unilateral commit and the retry recovery of global transactions in an autonomous MDBS environment. This notion makes it easier to ensure the isolation property of global transactions when the retry approach is applied. The formalization work illustrates that the conventional serializability and recoverability notions are not sufficient to specify the correct execution (i.e. isolated execution and recovery) of global transactions when the unilateral commit and the retry recovery are used to ensure the atomicity of global transactions. This work is significant because the unilateral commit and the retry recovery are an attractive complementary means to the undo recovery (whose correct schedule is specified by the conventional recoverability notion) for advanced transaction applications with the characteristics of site autonomy and long-lived execution     

An application-semantics-based relaxed transaction model for internetware

An internetware application is composed by existing individual services, while transaction processing is a key mechanism to make the composition reliable. The existing research of transactional composite service (TCS) depends on the analysis to composition structure and exception handling mechanism in order to guarantee the relaxed atomicity. However, this approach cannot handle some application-specific requirements and causes lots of unnecessary failure recoveries or even aborts. In this paper, we propose a relaxed transaction model, including system mode, relaxed atomicity criterion, static checking algorithm and dynamic enforcement algorithm. Users are able to define different relaxed atomicity constraint for different TCS according to application-specific require- ments, including acceptable configurations and the preference order. The checking algo- rithm determines whether the constraint can be guaranteed to be satisfied. The enforce- ment algorithm monitors the execution and performs transaction management work ac- cording to the constraint. Compared to the existing work, our approach can handle com- plex application requirements, avoid unnecessary failure recoveries and perform the transaction management work automatically.     

Transaction management issues in a failure-prone multidatabase system environment

This paper is concerned with the problem of integrating a number of existing off-the-shelf local database systems into a multidatabase system that maintains consistency in the face of concurrency and failures.The major difficulties in designing such systems stem from the requirements that local transactions be allowed to execute outside the multidatabase system control, and that the various local database systems cannot participate in the execution of a global commit protocol. A scheme based on the assumption that the component local database systems use the strict two-phase locking protocol is developed. Two major problems are addressed: How to ensure global transaction atomicity without the provision of a commit protocol, and how to ensure freedom from global deadlocks.     

Unifying concurrency control and recovery of transactions with semantically rich operations

The classical theory of transaction management contains two different aspects, namely concurrency control and recovery, which ensure serializability and atomicity of transaction executions, respectively. Although concurrency control and recovery are not independent of each other, the criteria for these two aspects were developed orthogonally and as a result, in most cases these criteria are incompatible with each other.

Recently a unified theory of concurrency control and recovery for databases with read and write operations has been introduced in [19, 1] that allows reasoning about serializability and atomicity within the same framework. In [19, 1] a class of schedules (called prefix reducible), which guarantees both serializability and atomicity in a failure prone environment with read/write operations was introduced. Several protocols were developed to generate such schedules by a database concurrency control mechanism.

We present here a unified transaction model for databases with an arbitrary set of semantically rich operations. We investigate constructive characterization of the class of prefix reducible schedules with semantically rich operations. It turns out that unlike databases with only read/write operations, the exact characterization of prefix reducible schedules in databases with arbitrary operations is rather infeasible. Thus, we propose here several sufficiently rich subclasses of prefix reducible schedules, and design concurrency control protocols that guarantee both serializability and atomicity for schedules from these classes.