ORACLE数据库服务器性能优化技术

ORACLE数据库的优化是通过合理分配计算机的资源(如内存、CPU、磁盘等)、调整系统运行参数来改进性能的过程,包括调整CPU参数、服务器内存分配、硬盘I/O、操作系统参数等几个部分.CPU使用率出现异常时要迅速找出原因,及时调整系统参数或优化SQL语句;内存参数的调整包括库缓冲区、数据字典缓冲区和缓冲区高速缓存的调整;影响磁盘I/O性能的主要原因有磁盘竞争、I/O次数过多和数据块空间的分配管理,使所有可用的磁盘均匀地平衡I/O,可以减少磁盘存取的时间;操作系统的调整要尽可能使ORA-CLE服务器使用资源最大化.在某单位"三流合一"项目中应用这些原则使服务器性能满足了系统的性能要求.     

ORACLE应用系统的性能参数分析与优化

基于ORACLE数据库应用系统的性能参数优化，根据实践归纳并提出调整服务器内存分配、调整磁盘I／O、调整资源竞争等具体方法，进行参数调整可提高系统运行效率1－5倍。对类似的应用系统具有实用参考价值。     

基于Oracle与ArcSDE的空间信息访问优化

在实际应用空间数据库管理方案中,逐步总结了与空间信息访问速度息息相关的数据库服务器配置和ArcSDE(American Sapatial Data Engine)空间数据库引擎配置两个主要方面的优化方法。通过调整组成SGA(System Global Area)的内存结构的大小,避免磁盘竞争、减少磁盘I／O次数,合理分配数据块空间,提高性能、确定回滚段数量,有利于频繁进行少量数据修改的联机事物处理、修改优先权,提高响应时间和竞争、调整索引格网单元整体优化空间数据的响应和系统性能等,形成了一套典型的空间信息访问优化方案。     

浅谈ORACLE数据库的性能优化

从内存、磁盘、CPU以及SQL语句4个方面阐述了ORACLE数据库的性能优化问题,以期对大型数据库管理具有一定的借鉴。     

Oracle数据库性能优化

从Oracle的结构出发,结合数据库管理与实践经验,对配置参数、内存结构、磁盘I／O、SQL语句等方面给出性能优化的策略。优化数据库性能,减少运行开销,达到提高运行性能的目的。     

采用内存数据访问对象提高数据库访问速度

将内存数据库的思想溶于传统磁盘数据库（DRDB）中，采用内存数据访问对象（MMDAO）技术，在当前主流计算机所能提供的有限内存中实现应用程序与数据库系统之间的接口，使数据库检索、存取等过程在内存中进行，避免大量的磁盘数据I／O，从而实现数据库应用程序中数据的高速存取、检索和操纵，提高应用系统的执行效率。     

应用控制的Web服务器磁盘缓冲方法

针对大数据负载时磁盘I／O阻塞造成的Web服务器性能下降的问题，提出了应用程序控制缓冲（ACC）方法．其核心是，缓冲跟踪模块根据应用程序的文件访问过程来跟踪内核中的文件缓冲状态，缓冲控制模块进行缓冲替换和预取，保持文件缓冲有足够的空闲空间．这样，服务器可在用户空间控制文件缓冲，从而准确判断文件是否在缓冲之中，并依此来调度请求，以提高处理器和磁盘的I／O并行度．同时，服务器可采用适应自身特点的缓冲和预读策略，以提高缓冲的命中率．作为示例，将ACC在Flash服务器中实现，实现中选用了“金字塔选择”缓冲算法．实验表明，在大数据负载下使用ACC的Flash服务器性能有很大的提高，即便在数据负载稍大于物理内存空间的情况下，服务器的吞吐率仍可提高约24．4％，而当数据负载超出物理内存2～3倍时，吞吐率可提高3～4倍。     

Oracle数据库的性能优化研究

对于数据库系统来说,磁盘I／O操作是数据库性能最重要的方面,它是计算机最大的开销。影响磁盘I／O性能的原因很多,本文重点研究了其中较重要的一个因素——磁盘竞争问题,主要从分离系统中的顺序I／O和分散随机I／O两个方面进行了探讨。     

内存优化漫谈

内存与CPU配合的好坏，直接影响电脑性能的发挥。利用操作系统对内存进行各种优化设置，可以使有限的内存得到最大程度的使用，从而提高CPU的利用率，提高电脑性能。     

关系数据库的优化设计研究

本文以数据库性能优化的基本原则为出发点,阐述了第三范式是数据库设计的重要原则,在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。     

Markedness and its Interpretation in Language Use

Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.     

Characterization of Ordovician carbonate reservoirs, southeastern Saskatchewan, Canada

The discovery of the prolific Ordovician Red River reservoirs in 1995 in southeastern Saskatchewan was the catalyst for extensive exploration activity which resulted in the discovery of more than 15 new Red River pools. The best yields of Red River production to date have been from dolomite reservoirs. Understanding the processes of dolomitization is, therefore, crucial for the prediction of the connectivity, spatial distribution and heterogeneity of dolomite reservoirs.The Red River reservoirs in the Midale area consist of 3～4 thin dolomitized zones, with a total thickness of about 20 m, which occur at the top of the Yeoman Formation. Two types of replacement dolomite were recognized in the Red River reservoir: dolomitized burrow infills and dolomitized host matrix. The spatial distribution of dolomite suggests that burrowing organisms played an important role in facilitating the fluid flow in the backfilled sediments. This resulted in penecontemporaneous dolomitization of burrow infills by normal seawater. The dolomite in the host matrix is interpreted as having occurred at shallow burial by evaporitic seawater during precipitation of Lake Almar anhydrite that immediately overlies the Yeoman Formation. However, the low δ18O values of dolomited burrow infills (-5.9‰～ -7.8‰, PDB) and matrix dolomites (-6.6‰～ -8.1‰, avg. -7.4‰ PDB) compared to the estimated values for the late Ordovician marine dolomite could be attributed to modification and alteration of dolomite at higher temperatures during deeper burial, which could also be responsible for its 87Sr/86Sr ratios (0.7084～0.7088) that are higher than suggested for the late Ordovician seawaters (0.7078～0.7080). The trace amounts of saddle dolomite cement in the Red River carbonates are probably related to "cannibalization" of earlier replacement dolomite during the chemical compaction.     

Features of Women's language

Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women＇s language from these perspectives： pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women＇s language, more attention should be paid to language use in social context. What＇s more, the linguistic phenomena in a speaking community can be understood more thoroughly.     

A computer generator for randomly layered structures

AcomputergeneratorforrandomlylayeredstructuresYUJia shun1,2,HEZhen hua2(1.TheInstituteofGeologicalandNuclearSciences,NewZealand;2.StateKeyLaboratoryofOilandGasReservoirGeologyandExploitation,ChengduUniversityofTechnology,China)Abstract:Analgorithmisintrod…     

低渗透非均质砂岩油藏启动压力梯度研究

理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。     

On Tragic Consciousness In The Works By Ernest Hemingway

As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.     

海南岛地体及其毗邻陆缘晚中生代—新生代古地磁研究和构造演化

本文叙述了对海南岛及其毗邻大陆边缘白垩纪到第四纪地层岩石进行古地磁研究的全部工作过程。通过分析岩石中剩余磁矢量的磁偏角及磁倾角的变化,提出海南岛白垩纪以来经历的构造演化模式如下:早期伴随顺时针旋转而向南迁移,后期伴随逆时针转动并向北运移。联系该地区及邻区的地质、地球物理资料,对海南岛上述的构造地体运动提出以下认识:北部湾内早期有一拉张作用,主要是该作用使湾内地壳显著伸长减薄,形成北部湾盆地。从而导致了海南岛的早期构造运动,而海南岛后期的构造运动则主要是受南海海底扩张的影响。海南地体运动规律的阐明对于了解北部湾油气盆地的形成演化有重要的理论和实际意义。     

An Index mechanism for multi-scale view in spatial databases

There are numerous geometric objects stored in the spatial databases. An importance function in a spatial database is that users can browse the geometric objects as a map efficiently. Thus the spatial database should display the geometric objects users concern about swiftly onto the display window. This process includes two operations:retrieve data from database and then draw them onto screen. Accordingly, to improve the efficiency, we should try to reduce time of both retrieving object and displaying them. The former can be achieved with the aid of spatial index such as R-tree, the latter require to simplify the objects. Simplification means that objects are shown with sufficient but not with unnecessary detail which depend on the scale of browse. So the major problem is how to retrieve data at different detail level efficiently. This paper introduces the implementation of a multi-scale index in the spatial database SISP (Spatial Information Shared Platform) which is generalized from R-tree. The difference between the generalization and the R-tree lies on two facets: One is that every node and geometric object in the generalization is assigned with a importance value which denote the importance of them, and every vertex in the objects are assigned with a importance value,too. The importance value can be use to decide which data should be retrieve from disk in a query. The other difference is that geometric objects in the generalization are divided into one or more sub-blocks, and vertexes are total ordered by their importance value. With the help of the generalized R-tree, one can easily retrieve data at different detail levels.Some experiments are performed on real-life data to evaluate the performance of solutions that separately use normal spatial index and multi-scale spatial index. The results show that the solution using multi-scale index in SISP is satisfying.     

《Chinese Science Bulletin》SUBJECT INDEX TO VOLUME 59(2014)

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Achieving Unusual States of Matter Under High Pressure

The elongation method,originally proposed by Imamura was further developed for many years in our group.As a method towards O(N)with high efficiency and high accuracy for any dimensional systems.This treatment designed for one-dimensional(ID)polymers is now available for three-dimensional(3D)systems,but geometry optimization is now possible only for 1D-systems.As an approach toward post-Hartree-Fock,it was also extended to