Database System Concepts ~ Introduction III

The architecture of a database system is greatly influenced by the underlying computer system on which the database system runs. Database systems can be centralized, or client-server, where one server machine executes work on behalf of multiple client machines. Database systems can also be designed to exploit parallel computer architectures. Distributed databases span multiple geographically separated machines. goalkeeper

Database System Concepts ~ Introduction II

Database systems are designed to manage large bodies of information. These large bodies of information do not exist in isolation. They are part of the operation of some enterprise whose end product may be information from the database or may be some device or service for which the database plays only a supporting role. autolater

Database System Concepts ~ Introduction I

A database-management system (DBMS) is a collection of interrelated data and a set of programs to access those data. The collection of data, usually referred to as the database, contains information relevant to an enterprise. The primary goal of a DBMS is to provide a way to store and retrieve database information that is both convenient and efficient.

Database systems are designed to manage large bodies of information. Management of data involves both defining structures for storage of information and providing mechanisms for the manipulation of information. In addition, the database system must ensure the safety of the information stored, despite system crashes or attempts at unauthorized access. If data are to be shared among several users, the system must avoid possible anomalous results. 继续阅读“Database System Concepts ~ Introduction I”

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Organizing the data for processing is an essential step in the development of a computer program. For many applications, the choice of the proper data structure is the only major decision involved in the implementation: once the choice has been made, the necessary algorithms are simple.

A data structure is not a passive object: We also must consider the operations to be performed on it (and the algorithms used for these operations). This concept is formalized in the notion of a data type. 继续阅读“Elementary Data Structures ~ Building Blocks”

信号完整性小记 ~ 时域与频域

在前文 信号完整性小记 ~ 概述 中指出分析和表征信号完整性,分为时域和频域两种途径和手段。时域是根本,可以用示波器观察信号波形的失真和眼图,找出 pin-to-pin 的时延、错位、抖动、噪声、过冲/下冲及建立/保持时间等,选用的仪器有 TDR(Time Domain Reflectometry)。频域是用频谱分析仪观察分析信号的波形,通常用于信号噪声的带宽分析、噪声抑制度量及 EMI 量级分析,仪器有 VNA 和 阻抗分析仪 IA 继续阅读“信号完整性小记 ~ 时域与频域”

信号完整性小记 ~ 概述

在前文 信号完整性小记 ~ 前言 中已对信号完整性定义以及根源等基本问题进行了小结,本文在回顾前文的基础上对相关具体概念进行阐述,为后续分析讨论提供支持。 816-592-1052

CentOS 7 安装ossfs挂载oss文件系统

ossfs挂载可以理解为把挂载的Bucket当作一个ECS目录来操作,存储文件到挂载的Bucket中是占用的这个Bucket的内存,不会占用ECS的内存。对象存储 OSS 基本概念可点击☞☞☞☞ Sussex pig 查看基本概念介绍。由于 OSS 与文件系统存在显著的差异,故官方文档不建议将 OSS 映射为文件系统。如果非要这样做,最好尽量只做写新文件、删除文件、读取文件这几种操作。使用 OSS 应该充分发挥其优点,即海量数据处理能力,优先用来存储海量的非结构化数据,比如图片、视频、文档等。本文反其道而行之只是为了更加方便的查看和操作,存储的内容确实都是图片、视频、文档等,没有埋没的它的天性。 继续阅读“CentOS 7 安装ossfs挂载oss文件系统”

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在前文 (604) 275-3487 中监控 Linux 资源时,输入 top 命令后,发现内存相关 Mem 和 Swap 的 Buffer 和 Cache,觉得有必要深入了解下,故此对其做个小结。 610-857-0682

(314) 441-6691

Grep 这个命令是一个全局查找正则表达式并且打印结果行的命令。它的输入是一个文件或者是一个标准输入(stdin),或者是一个“-”连字符等。它的输出一般是打印在屏幕上。Grep家族里还有 egrep 和 fgrep 这两个命令,本文不赘述。 6055167159