Transactions and versioning in an ODBMS

Versant Object Technology builds and sells a distributed Object Database Management System (ODBMS), called VERSANT. This position paper proposes transaction model and version model requirements in support of the kinds of distributed database processing that ODBMS applications require. Transaction model requirements address the long transactions required by many ODBMS applications, as well as the short transactions found in conventional DBMS products. Version model requirements suggest a minimal set of primitives which can be extended to support emerging standards and companies' specific models.     

Cooperative transaction hierarchies: Transaction support for design applications

Traditional atomic and nested transactions are not always well-suited to cooperative applications, such as design applications. Cooperative applications place requirements on the database that may conflict with the serializability requirement. They require transactions to be long, possibly nested, and able to interact with each other in a structured way. We define a transaction framework, called acooperative transaction hierarchy, that allows us to relax the requirement for atomic, serializable transactions to better support cooperative applications. In cooperative transaction hierarchies, we allow the correctness specification for groups of designers to be tailored to the needs of the application. We usepatterns andconflicts to specify the constraints imposed on a group's history for it to be correct. We also provide some primitives to smooth the operation of the members. We characterize deadlocks in a cooperative transaction hierarchy, and provide mechanisms for deadlock detection and resolution. We examine issues associated with failure and recovery.     

The CORBA Activity Service Framework for supporting extended transactions

Although it has long been realized that ACID (atomicity, consistency, isolation, durability) transactions by themselves are not adequate for structuring long‐lived applications and much research work has been done on developing specific extended transaction models, no middleware support for building extended transactions is currently available and the situation remains that a programmer often has to develop application specific mechanisms. The CORBA Activity Service Framework described in this paper is a way out of this situation. The design of the service is based on the insight that the various extended transaction models can be supported by providing a general purpose event signalling mechanism that can be programmed to enable activities—application specific units of computations—to coordinate each other in a manner prescribed by the model under consideration. The different extended transaction models can be mapped onto specific implementations of this framework, permitting such transactions to span a network of systems connected indirectly by some distribution infrastructure. The framework described in this paper is an overview of the OMG's (Object Management Group) Additional Structuring Mechanisms for the OTS standard. Through a number of examples the paper shows that the framework has the flexibility to support a wide variety of extended transaction models. Although the framework is presented here in CORBA specific terms, the main ideas are sufficiently general, so that it should be possible to use them in conjunction with other middleware. Copyright © 2003 John Wiley & Sons, Ltd.     

Application Specific Transaction Management in Multidatabase Systems

We present a transaction model for multidatabase systems with autonomous component systems, coined heterogeneous 3-level transactions. It has become evident that in such a system the requirements of guaranteeing full ACID properties and full local autonomy can not be reconciled. In the heterogeneous 3-level transaction model, semantics of actions and specific properties of the architecture of multidatabase systems and of applications are utilized to define application specific compromises between these competing goals. We consider different definitions of conflicts between actions together with application specific sets of allowed (autonomous) local transactions and global subtransactions. A formal model for serializability is given. It is proven that heterogeneous 3-level transactions guarantee all consistency constraints that are ensured in serial executions. In contrast to most other models, we do not require data to be partitioned into global and local data. In particular, heterogeneous 3-level transactions even allow the same data to be updated by local and global transactions in parallel, if these updates are found to be semantically non-conflicting. Recovery is handled by inverse actions. We present a formal framework for this approach which is fully integrated into serializability theory by considering inverse actions as ordinary actions. This has an important impact on the relationship of concurrency control and recovery in our model: By changing the definition of conflicts between actions in order to tailor the model according to application needs, recovery is implicitly affected and no further explicit adaptation of recovery algorithms is necessary. The heterogeneous 3-level transaction model assumes component database systems to support ACID transaction properties. Further properties of local transactions or interfaces of the component database systems are not required. We describe a prototype implementation of heterogeneous 3-level transactions in the object-oriented database system VODAK.     

Analysis of dependencies in advanced transaction models

Transactional dependencies play an important role in coordinating and executing the subtransactions in advanced transaction processing models, such as, nested transactions and workflow transactions. Researchers have formalized the notion of transactional dependencies and have shown how various advanced transaction models can be expressed using different kinds of dependencies. Incorrect specification of dependencies can result in unpredictable behavior of the advanced transaction, which, in turn, can lead to unavailability of resources and information integrity problems. In this work, we focus on how to correctly specify dependencies in an advanced transaction. We enumerate the different kinds of dependencies that may be present in an advanced transaction and classify them into two broad categories: event ordering and event enforcement dependencies. Different event ordering and event enforcement dependencies in an advanced transaction often interact in subtle ways resulting in conflicts and redundancies. We describe the different types of conflicts that can arise due to the presence of multiple dependencies and describe how one can detect such conflicts. An advanced transaction may also contain redundant dependencies—these are dependencies that can be logically derived from other dependencies. We show how such extraneous dependencies can be eliminated to get an equivalent set of dependencies that has the same effect as the original set. Our dependency analysis is done in the context of a generalized advanced transaction model that is capable of expressing different kinds of advanced transactions. Recommended by: Amit Sheth     

On Concurrency Control in Multidatabase Systems with an Extended Transaction Model

A major concurrency control problem that we have to cope in multidatabase systems is the global deadlock detection and resolution problem. This detection must take into account the autonomy of local systems, which make impossible the visibility of the state of local transactions. A well-known approach to detect such deadlocks, called potential global deadlocks, is one based on the potential conflict graph (PCG) appropriate for the multidatabase transaction model with a global commit protocol. This classical transaction model is very constraining for applications manipulating great volumes of information, and where subtransaction terminations (commit or abort) of global transactions are not totally dependant. In this paper we present an effective potential global deadlock characterization, and an efficient potential global deadlock detection algorithm, in multidatabase systems with an extended transaction model more suited for such applications.     

事务工作流WfSaga及其建模工具

以扩展事务模型Saga和Flexible为基础,引入可替换事务和平凡事务等事务种类,借用传统事务恢复机制"保存点"的思想,提出了支持分布式工作流应用的可靠事务工作流模型WfSaga,以Java图形操作为基础,设计了图形化建模工具并用基于XML的过程定义语言对模型进行了描述,最后对模型的正确性验证进行了讨论.     

A survey on the history of transaction management: from flat to grid transactions

Transactions have been around since the Seventies to provide reliable information processing in automated information systems. Originally developed for simple ‘debit-credit’ style database operations in centralized systems, they have moved into much more complex application domains including aspects like distribution, process-orientation and loose coupling. The amount of published research work on transactions is huge and a number of overview papers and books already exist. A concise historic analysis providing an overview of the various phases of development of transaction models and mechanisms in the context of growing complexity of application domains is still missing, however. To fill this gap, this paper presents a historic overview of transaction models organized in several ‘transaction management eras’, thereby investigating numerous transaction models ranging from the classical flat transactions, via advanced and workflow transactions to the Web Services and Grid transaction models. The key concepts and techniques with respect to transaction management are investigated. Placing well-known research efforts in historical perspective reveals specific trends and developments in the area of transaction management. As such, this paper provides a comprehensive, structured overview of developments in the area.     

Automatic Transaction Compensation for Reliable Grid Applications

Abstract As grid technology is expanding from scientific computing to business applications, service oriented grid computing is aimed at providing reliable services for users and hiding complexity of service processes from them. The grid services for coordinating long-lived transactions that occur in business applications play an important role in reliable grid applications. In this paper, the grid transaction service （GridTS） is proposed for dealing with long-lived business transactions. We present a compensation-based long-lived transaction coordination algorithm that enables users to select results from committed sub-transactions. Unlike other long-lived transaction models that require application programmers to develop corresponding compensating transactions, GridTS can automatically generate compensating transactions on execution of a long-lived grid transaction. The simulation result has demonstrated the feasibility of GridTS and effectiveness of the corresponding algorithm.     

关于实时数据库事务

实时数据库事务显示了与传统数据库事务的很大不同．这些不同主要表现在事务的复杂结构、定时特性、相关性和正确性方面．本文先分析了实时数据库事务的应用特征与需求，并给出了一个复杂事务结构的框架，然后着重讨论实时事务间的相关性：结构相关、数据相关、行为相关，以及实时事务的结果、结构、行为及时间正确性．