小布老师讲座笔记（一）

IT产业的基本形式：
微软流派 非微软流派
操作系统
数据库
应用服务器
应用软件
Linux/Unix 设计哲学：制作一个稳定可靠的操作系统，概念简单，设计可靠。
Windows: 设计哲学：让普通人都可以方便地使用计算机
Linux内核：www.kernel.org
Redhat系列发行版本
CentOS系列：免费的RedHat
Ubuntu(主要面向客户端，华丽界面), debian ,Mandriva, SuSE, Slackware, Knoppix, gentoo…..
VMware产品分为：VMWare Workstation 和VMWare Server
FTP服务：
FTP就是file transfer protocol, 用来下载或者上传文件数据的协议，会话时使用两个通道，一个叫控制通道(21端口)，一个叫数据通道(20端口)
目前最高效最安全的ftp服务器是Vsftp
Vsftp(Very Secure FTP)是一种在Unix/Linux中非常安全且快速稳定的FTP服务器，目前已经被许多大型站点所采用。
Vsftpd的实现有三种方式：
1. 匿名用户形式：在默认安装的情况下，系统只提供匿名用户访问
2. 本地用户形式：以/etc/passwd中的用户名为认证方式
3. 虚拟用户形式：支持将用户名和口令保持在数据库文件或数据库服务器中。相对于FTP的本地用户形式来说，虚拟用户只是FTP服务器的专有用户，虚拟用户只能访问FTP服务器所提供的资源，这大大增强系统本身的安全性。相对于匿名用户而言，虚拟用户需要用户名和密码才能获取FTP服务器中的文件，增加了对用户和下载的可关联性，对于需要提供下载服务，但又不希望所有人都可以匿名下载：既需要对下载用户进行管理，又考虑到主机的安全和管理方便的FTP站点来说，虚拟用户是一种极好的解决方案。
Oracle 9i DBA Fundamentals training
Outline the Oracle Architecture and its main components

OV of Primary Components

Archived Log files

Redo LOg

Control

Data files

DataBase

Parameter file

Password file

Large Pool

Redo Log Buffer

Java Pool

Data Dictionary

Library Cache

Shared Pool

S GＡ

Instance

User process

file

Server process

P G A

file

file

PMON

SMON

DWR

LGWR

Database Buffer Cache

An Oracle server :
Is a database management system that provides an open, comprehensive , integrated approach to information management
Consists of oracle instance and an oracle database
An Oracle instance :
Is a means to access an oracle database,lways opens one and only one database Consists of memory and background process structures
Connecting to an Oracle instance:
Establishing a user connection
Creating a session
Oracle Database
An Oracle database:
Is a collection of data that is treated as an unit
Consists of three file types data file control file redo file
Memory Structure
Oracle’s memory structure consists of two memory areas known as:
·System Global Area(SGA): Allocated at instance start
up,and is a fundamental component of an Oracle instnce
SGA is implements by share memory:
find command:
ipcs or show sga;
Program Global Area(PGA):Allocated when the server
process is started
The SGA consists of several memory structures
★ Shared Pool
★ Database Buffer Cache
★ Redo Log Buffer
★ Other structures(for example, lock and latch)
management, statistical data)
★ There are two additional memory structures that
can be configured within the SGA:
-Large Pool
-Java Pool
SGA
★ Is dynamic
★ Sized by the SGA_MAX_SIZE parameter
★ Allocated and tracked in granules by SGA components
★ Contiguous virtual memory allocation
★ Granule size based on total estimated SGA_MAX_SIZE
find Granule command:
SQL> select component, granule_size from v$sga_dynamic_components
COMPONENT GRANULE_SIZE
---------------------------------------------------------------- ------------
shared pool 4194304
large pool 4194304
java pool 4194304
streams pool 4194304
DEFAULT buffer cache 4194304
KEEP buffer cache 4194304
RECYCLE buffer cache 4194304
DEFAULT 2K buffer cache 4194304
DEFAULT 4K buffer cache 4194304
DEFAULT 8K buffer cache 4194304
DEFAULT 16K buffer cache 4194304

COMPONENT GRANULE_SIZE
---------------------------------------------------------------- ------------
DEFAULT 32K buffer cache 4194304
ASM Buffer Cache 4194304
13 rows selected.
Shared Pool:
● Used to store:
—Most recently executed SQL statements
—Most recently used data definitions
● It consists of two key performance-related
memory structures:
—Library Cache
—Data Dictionary Cache
● Sized by the parameter
SHARED_POOL_SIZE
change pool size:
ALTER SYSTEM SET SHARED_POOL_SIZE = 64M;
Library Cache
Stores information about the most recently used SQL and PL/SQL statements
Enables the sharing of commonly used statements
Is managed by a least recently used(LRU) algorithm
Consists of two structures:
—Shared SQL area
—Shared PL/SQL area
Data Dictionary Cache
A collection of the most recently used definitions in the database.
Includes information about database files,tables, indexes, columns, users, privileges, and other database objects.
Database Buffer Cache
—Stores copies of data blocks that have been retrieved from the data files
—Enables great performance gains when you obtain and update data
—Managed through an LRU algorithm
—DB_BLOCK_SIZE determines primary block size
Consists of independent subcaches:
—DB_CACHE_SIZE
—DB_KEEP_CACHE_SIZE
—DB_RECYCLE_CACHE_SIZE
Can be dynamically resized
ALTER SYSTEM SET DB_CACHE_SIZE = 96M;
Redo Log Buffer
Records all changes made to the database data blocks
Primary purpose is recovery
Size defined by LOG_BUFFER
Large Pool
An optional area of memory in the SGA
Relieves the burden placed on the Shared Pool
Used for:
—Session momory(UGA) for the Shared Server
—I/O server processes
—Backup and restore operations or RMAN
—Parallel execution message buffers
Java Pool
—Services parsing requirements for Java command
—Required if installing and using Java
—Sized by JAVA_POOL_SIZE parameter
PGA: Program Global Area
—Memory reserved for each user
process connecting to an Oracle database
—Allocated when a process is created
—Deallocated when the process is termitated