数据库应用系统性能与数据查询优化

数据库查询的效率是数据库应用系统性能的重要指标，本文好数据查询优化的几种方式，并以实例说明查询优化的过程及其在数据库应用系统中的应用。     

基于SQL数据库的性能优化问题分析

随着数据库应用系统中数据的增加,效率是将是数据库应用开发与管理过程中必须解决的主要问题。因此必须对数据库进行优化。其中既包括了对逻辑数据库设计的优化、物理数据库硬件的优化、服务器硬件平台性能的优化、以及SQL语句本身查询的优化。本文通过对SQL Server数据库应用中影响效率的主要问题进行相应的分析,给出了数据库的性能优化方法,从而提高了整个数据库的运行效率。     

Oracle数据库性能优化技术

Oracle数据库足当前应用最广泛的大型数据库之一，而其性能优化直接关系到系统的正常运行效率。该以数据库性能优化的基本原则为出发点，阐述了在数据库设计阶段如何避免竞争和如何优化数据访问，在数据库运行阶段如何从操作系统和数据库实例级别上调整内存和I/O来达到数据库性能优化的各种技术。     

基于Oracle 9i数据库的查询优化

数据库的任务是存储和管理数据，而用户能看到的有关数据库特性就是它的性能，数据库的查询操作是影响一个应用系统响应时间的关键因素。科学合理地构造查询系统，是成功开发数据库应用系统非常重要的环节。该文主要介绍Oracle 9i的查询优化程序及其组成，从基于索引、SQL优化、以及其它措施各个方面阐述了Oracle 9i数据库查询效率提高的经验和方法。     

基于 Oracle 数据库电信 CRM 经营分析系统的性能优化*

数据库性能的优化在基于O racle数据库的应用系统开发过程中至关重要,论文讨论基于O racle数据库电信CRM经营分析系统的性能优化技术,包括SQL语句优化,索引优化,分区技术以及Oracle内存优化技术。分析测试表明：应用这些优化策略,系统的响应时间明显降低,系统的效率得到提升,整个系统使用性能达到了最优状态。     

Delphi＋SQL Server 2000平台数据库应用系统研究

当数据量达到一定程度时,数据库应用系统就会出现瓶颈.这将导致系统可靠性降低、使用效率低下.对Microsoft SQL Server 2000数据应用库系统进行了深入研究,分析了数据库应用系统的时间开销.重点分析了基于索引的数据库优化和数据库分页算法优化.通过实验验证了所提出的方案是可行的,优化算法是高效且可靠的.     

MIS数据库性能优化

针对MIS数据库中普遍存在的效率问题，对影响数据库性能的相关因素进行了分析，提出了性能优化的方法和途径。优化数据库是一个系统工程，若单纯注重某一方面的优化不能取得整体效果，应将效率意识贯穿于应用开发的全过程。     

Oracle数据库性能优化技术在邮政系统中的应用

Oracle数据库在邮政行业应用越来越广泛,而其性能优化直接关系到邮政应用系统的运行效率。本文以数据库性能优化的基本原则为出发点,阐述了在数据库设计阶段如何避免竞争和如何优化数据访问,在数据库运行阶段如何从操作系统和数据库实例级别上调整内存和I/O来达到数据库性能优化的各种技术。     

基于Oracle数据库性能优化技术研究

Oracle数据库性能直接影响到Oracle数据库应用系统的运行效率,文章首先简要介绍了Oracle数据库性能优化的目标,然后分析了影响Oracle数据库系统性能的因素,接着详细介绍了数据库的优化、内存优化、I/O优化和SQL语句优化技术,最后通过实验证明,经过优化后,Oracle数据库性能得到了改善和提高。     

Oracle数据库性能优化技术在邮政系统中的应用

Oracle数据库在邮政行业应用越来越广泛,而其性能优化直接关系到邮政应用系统的运行效率.本文以数据库性能优化的基本原则为出发点,阐述了在数据库设计阶段如何避免竞争和如何优化数据访问,在数据库运行阶段如何从操作系统和数据库实例级别上调整内存和I/O来达到数据库性能优化的各种技术.     

Effect of project characteristics on project performance in construction projects based on structural equation model

Most past studies that analyze project performance and the characteristics that affect such performance consist of a simple form, in which they present the brief relationship between project performance and a few characteristics that affect it. Furthermore, due to the limitations of the research methodologies used in these studies, important characteristics were often not considered in developing the relationship between project performance and project characteristics. This study aims to analyze the overall relationship between project performance and a project’s characteristics. This study deduced (i) the overall causal relationship and (ii) the degree of influence between 17 project characteristics and five project performance indices. In order to achieve this goal, this study employed the factor analysis method and a structural equation model (SEM). In addition, this study established a SEM based on quantitative data from actual case studies as opposed to previous SEM studies that mainly use qualitative data.The SEM developed in this study can identify the project characteristics that affect the level of project performance required by owner in the planning stage, and is thus expected to help facilitate the decision-making process in the early planning stage of a project.     

语义缓存的聚集查询匹配研究

为提高海量数据库系统的查询效率，围绕海量数据库系统中的聚集查询技术，把通常应用于小型数据库查询的语义缓存技术拓展到海量数据库的聚集查询中．首先研究了面向聚集查询的语义缓存形式化描述，在此基础上讨论了利用缓存处理查询的条件并对查询匹配进行了分类，提出并实现了包含匹配判定算法和相交匹配判定算法，最后给出了相应的实验结果．在某大型实际工程中的应用表明上述判定算法是有效的．     

Evaluating the Contributions of a Structured Software Development and Maintenance Methodology

This study evaluates a vendor supplied structured software development and maintenance methodology (SDMM) which was implemented in a large manufacturing firm. Thirty project teams using the methodology are measured for contributions to IS productivity compared to teams using no methodology. The performance of these projects is evaluated using both objective metrics and subjective measures taken from stakeholders of the software applications. The performance results of these thirty systems are then contrasted to the performance results of thirty-five applications in the same firm that do not use this SDMM and to one hundred sixteen applications across eleven other organizations. All of these applications had been in operation at least six months when they were studied. The software systems developed and maintained using the SDMM were found to have some significant cost and quality performance gains over the applications that do not use a methodology. However, these systems were found to have lower levels of configuration management, a feature not found within the methodology.     

基于类推和灰色模型的软件阶段成本预测

准确预测软件成本是软件工程领域最具挑战性的任务之一。软件开发固有的不确定性和风险性,使得仅仅在项目早期预测总成本是不够的,还需要在开发过程中持续预测各个阶段的成本,并根据变化趋势重新分配资源,以确保项目在规定的时间和预算内完成。由此,提出一种基于类推和灰色模型的软件阶段成本预测方法——AGSE(Analogy & Grey Model Based Software Stage Effort Estimation)。该杂交方法通过合并两种方法的预测值得到最终的预测结果,避免了单独使用其中一种方法预测时存在的局限性。在真实的软件项目数据集上的实验结果表明,AGSE的预测精度优于类推方法、GM(1,1)模型、GV方法、卡尔曼滤波和线性回归,显示出较大的潜力。     

互联网应用性能测量系统的研究与实现

致力于建立互联网应用网络性能的基础性测量平台,它为互联网上众多的应用系统提供了一个分布式可扩展的性能测量系统,首先分析了应用系统性能数据的数据特征,并将性能数据划分为3类数据集,建立了互联网应用系统网络性能测量模型,并针对应用网络性能测量数据获取的难点,提出了应用探针和区域探针的分布式体系结构,最后结合海量信息系统测量平台的研究,给出了该模型的具体实现技术。     

How mobile phones perform in collaborative augmented reality (CAR) applications

This paper presents the experimental analysis of mobile phones for Augmented Reality marker tracking, a core task that any CAR application must include. The results show that the most time consuming stage is the marker detection stage, followed by the image acquisition stage. Moreover, the rendering stage is decoupled on some devices, depending on the operative system used. This decoupling process allows avoiding low refresh rates, facilitating the collaborative work. However, the use of multicore devices does not significantly improve the performance provided by CAR applications. Finally, the results show that unless a poor network bandwidth makes the network to become the system bottleneck, the performance of CAR applications based on mobile phones will be limited by the detection stage. These results can be used as the basis for an efficient design of CAR systems and applications based on mobile phones.     

A knowledge-based evolutionary assistant to software development project scheduling

The scheduling of software development projects is a central, non-trivial and costly task for software companies. This task is not exempt of erroneous decisions caused by human limitations inherent to project managers. In this paper, we propose a knowledge-based evolutionary approach with the aim of assisting to project managers at the early stage of scheduling software projects. Given a software project to be scheduled, the approach automatically designs feasible schedules for the project, and evaluates each designed schedule according to an optimization objective that is priority for managers at the mentioned stage. Our objective is to assign the most effective set of employees to each project activity. For this reason, the evaluation of designed schedules in our approach is developed based on available knowledge about the competence of the employees involved in each schedule. This knowledge arises from historical information about the participation of the employees in already executed projects. In order to evaluate the performance of our evolutionary approach, we present computational experiments developed over eight different sets of problem instances. The obtained results are promising since this approach has reached an optimal level of effectivity on seven of the eight mentioned sets, and a high level of effectivity on the remaining set.     

Pre-project partnering impact on an information system project,project team and project manager

Information system (IS) managers have long recognised the need to use project management approaches in the design and delivery of their system development projects. The result has been the widespread use of project teams headed by a project leader or manager. However, given the fact that there has been a low success rate for IS projects, there is a growing need to seek out new methods and controls for projects. One approach involves the practice of altering the project environment prior to the commencement of project tasks. To determine whether such pre-project activities may be effective, a model is proposed and tested relating the activities to the performance of the project manager and characteristics of an effective project team. Data from a sample of 186 project team members indicate that the pre-project activities lead to more effective teams and managers and eventually to project success. Thus, it is important that organisations begin work on projects at an earlier stage.