Performance of B+ tree concurrency control algorithms

A number of algorithms have been proposed to access B⁺-trees concurrently, but they are not well understood. In this article, we study the performance of various B⁺-tree concurrency control algorithms using a detailed simulation model of B⁺-tree operations in a centralized DBMS. Our study covers a wide range of data contention situations and resource conditions. In addition, based on the performance of the set of B⁺-tree concurrency control algorithms, which includes one new algorithm, we make projections regarding the performance of other algorithms in the literature. Our results indicate that algorithms with updaters that lock-couple using exclusive locks perform poorly as compared to those that permit more optimistic index descents. In particular, the B-link algorithms are seen to provide the most concurrency and the best overall performance. Finally, we demonstrate the need for a highly concurrent long-term lock holding strategy to obtain the full benefits of a highly concurrent algorithm for index operations.     

一种改进的并行连接算法Diag-Join及其性能分析

介绍了一种改进的并行连接算法：Diag-Join算法，并将它运用到并行环境中。实验表明，Diag-Join算法在内存足够时可以取得最好的性能，即使在内存较小的情况下，仍能得到令人满意的效果。     

Dreamweaver UltraDev ＆ ASP技术在动力环境集中监控系统二次开发中的应用

动力环境集中监控系统的用户在使用过程中，往往结合自身需要提出一些特定的要求，但目前监控产品厂家所提供的软件却又不足以支持这些功能。文中结合实例，介绍了在Dreamweaver UltraDev开发环境下利用ASP技术，从动力监控系统的大型数据库中获取数据，自动生成报表的方法。这种方法无疑是一种有效、简洁的设计方法。实践证明该方法对于加强监控系统的例行维护管理具有重要的现实意义。     

Design and coding considerations of the soil data language interpreter

A query language, named Soil Data Language (SDL), for retrieving information from a Soil. Data Bank, is part of the ARSIS (A Relational Soil Information System) system, currently being developed in Greece. The interpreter of the language accepts input programs, expressed as SDL commands, and outputs the requested information. This paper describes design principles employed during the coding of the interpreter of the language. The derived program can be modified to cover eventual alterations to the specifications of language or the content and structure of the data bank. The study may be seen as an initiative to the design of Generalized Soil and Land Information Systems that primarily are concerned with the easy adaptation to a variety of National processing requirements.     

RER： A Replica Efficiency Based Replication Strategy

The technology of replication is often used in the unstructured Peer-to-peer （P2P） systems to allocate more replicas for the hot spots in order for a higher search performance. But the questions that what is the optimal number of copies for each file and what is the practicable approach to the optimal number are seldom answered in the related works. In terms of success rate, this paper firstly investigates the optimal allocation of copies for each file according to query rate with the routing algorithm of random walks. Then a practicable method is proposed to approach the optimal allocation in the unstructured P2P systems. Our results offer a new understanding of replication and our work contributes much to the content distribution in the Internet environment.     

Characterization of Bandwidth-Aware Meta-Schedulers for Co-Allocating Jobs Across Multiple Clusters

In this paper, we present a bandwidth-centric job communication model that captures the interaction and impact of simultaneously co-allocating jobs across multiple clusters. We compare our dynamic model with previous research that utilizes a fixed execution time penalty for co-allocated jobs. We explore the interaction of simultaneously co-allocated jobs and the contention they often create in the network infrastructure of a dedicated computational multi-cluster.We also present several bandwidth-aware co-allocating meta-schedulers. These schedulers take inter-cluster network utilization into account as a means by which to mitigate degraded job run-time performance. We make use of a bandwidth-centric parallel job communication model that captures the time-varying utilization of shared inter-cluster network resources. By doing so, we are able to evaluate the performance of multi-cluster scheduling algorithms that focus not only on node resource allocation, but also on shared inter-cluster network bandwidth.     

对质监系统电子政务工作的思考

信息技术的发展,不仅推动了商业、教育等领域的发展,同时也加速了政府信息化的进程,电子政务应孕而生。其中信息查询服务及电子监管服务是电子政务的一个重点。     

OBS网络中偏射路由的研究

目前光突发交换（OBS）技术作为下一代光互联骨干网最有前途的交换方式受到广泛关注。偏射路由是一种有效的竞争解决方案。根据已有的研究,首先介绍了偏射路由的概念;然后探讨了偏射路由解决方案的关键问题,如偏射路由时间、控制分组的格式、节点的功能模块和实现算法;最后将偏射路由与其他竞争解决方案进行了比较。     

基于FDL和TWC的光突发竞争解决方案及性能分析

在光突发交换(OBS)网络中,突发竞争是影响网络性能的一个重要因素,因此如何有效地解决它,成了OBS网络非常重要的问题.在分析当前文献中的解决方案的优缺点后,提出了一种突发竞争解决方案的系统实现.该实现将光纤延迟线(FDL)时城缓存与波长转换器(TWC)波长变换、空城技术结合在一起,构造了一个基于前向转发缓存和反馈循环缓存的两级交换结构.最后从多方面对该系统实现的竞争解决有效性进行了性能分析和计算机仿真,结果表明:它在适当的业务强度(小于0.6)下,能有效改善突发丢失率和突发延迟;同时能降低系统所需的光器件数目.     

中间件在信息查询优化系统中的应用

提出了基于中间件的数据查询优化模型系统,以中间件和分布式系统为理论基础,以曾经开发过的MIS系统为例介绍这种数据查询的结构模型和实现方法,该系统满足了用户的分布式系统的要求,查询条件能够自动灵活地生成,增加了实用性,提高了数据库的执行效率。