技術解説 IEEE Computer

Processes are increasingly being used to make complex application logic explicit. Programming using processes has significant advantages but it poses a difficult problem from the system point of view in that the interactions between processes cannot be controlled using conventional techniques. In terms of recovery, the steps of a process are different from operations within a transaction. Each one has its own termination semantics and there are dependencies among the different steps. Regarding concurrency control, the flow of control of a process is more complex than in a flat transaction. A process may, for example, partially roll back its execution or may follow one of several alternatives. In this article, we deal with the problem of atomicity and isolation in the context of processes. We propose a unified model for concurrency control and recovery for processes and show how this model can be implemented in practice, thereby providing a complete framework for developing middleware applications using processes.

Atomicity and isolation for transactional processes

This thesis therefore addresses the question how current transaction management theory can be improved such that these novel applications can be better supported by transaction management. The approach taken in this thesis is to exploit more semantics of the particular application than in existing approaches. We exploit application semantics to improve concurrency and application semantics to improve recovery.

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Improving Concurrency and Recovery in Database Systems by Exploiting Application Semantics

A transaction of processing a database distributed to a plurality of servers in a chain of local transactions individually processed by and in each server. In each server, when the processing of a local transaction in the server is completed, the local transaction is committed or rolled back, and the right to execute a process of an application is released. Until all chained transactions are completed, the exclusive control of data accessed in the local transactions and the data before update of updated data is managed in a log, thereby guaranteeing the consistency and integrity of the data.

Transaction processing method, transaction control apparatus and program thereof

Task scheduling plays a vital role in distributed computing. It enhances the performance of the system as it minimizes the overall execution time and reduces overhead problems like communication delay by allocating suitable task to appropriate processor. Different scheduling techniques are discussed in this paper which are employed for task scheduling. Taxonomy of hierarchical classification is discussed for concurrent system and further several task scheduling algorithms are described on the basis of dependency and approach used such as static or dynamic for low throughput and efficient performance.

A Survey on Scheduling Algorithms for Parallel and Distributed Systems

A heterogeneous distributed database environment integrates a set of autonomous database systems to provide global database functions. A flexible transaction approach has been proposed for the heterogeneous distributed database environments. In such an environment, flexible transactions can increase the failure resilience of global transactions by allowing alternate (but in some sense equivalent) executions to be attempted when a local database system fails or some subtransactions of the global transaction abort. We study the impact of compensation, retry, and switching to alternative executions on global concurrency control for the execution of flexible transactions. We propose a new concurrency control criterion for the execution of flexible and local transactions, termed F-serializability, in the error-prone heterogeneous distributed database environments. We then present a scheduling protocol that ensures F-serializability on global schedules. We also demonstrate that this scheduler avoids unnecessary aborts and compensation.

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M. Nodine

Papers

Global scheduling for flexible transactions in heterogeneous distributed database systems