Oracle 11g XE 是 Oracle 数据库的免费版本

Oracle 11g XE 是 Oracle 数据库的免费版本，支持标准版的大部分功能，11g XE 提供 Windows 和 Linux 版本。

做为免费的 Oracle 数据库版本，XE 的限制是：

• 最大数据库大小为 11 GB
• 可使用的最大内存是 1G
• 一台机器上只能安装一个 XE 实例
• XE 只能使用单 CPU，无法在多CPU上进行分布处理

下面介绍安装过程： 
首先下载 Oracle 11g XE 并解压，解压后的DISK1目录中包含了 setup.exe 文件，双击启动安装程序，首先会显示一个协议信息，点击继续安装：

• 操作系统至少是 Windows XP
• 当前操作用户必须有管理员权限
• 当前机器尚未安装 XE

选择安装目录：
 
设置数据库密码： 

前面几步过后会显示一个安装概要信息，包含以下内容：

• 侦听器端口: 1521
• MTS 服务端口: 2030
• HTTP 侦听端口: 8080

接下来看看 XE 在我们的系统中安装了什么？

服务详细列表：

• OracleServiceXE
  This is the actual database engine.
• OracleXETNSListener
  This service is responsible for listening incoming connections and passing successful connections to the database engine. Note, that if this service is down, you won’t be able to connect to the database remotely. Existing connections won‘t be affected.
• OracleJobSchedulerXE
  This service is used when external jobs are run. By default it is disabled. If you plan to run external jobs (such as executables, batches etc), modify the account the service uses to use proper, low-privileged credentials and start the service.
• OracleXEClrAgent
  On Windows platforms Oracle offers CLR integration. Since a CLR operation is run using an extproc process, it’s normally done using a dedicated (single threaded)extproc for a single session. This may not be the optimal way to handle CLR calls. ClrAgent provides a multi-threaded mechanism so that a single extproc process may serve several CLR calls.
• OracleMTSRecoveryService
  This one is responsible of resolving in-doubt transactions when Oracle is participating in distributed transactions with Microsoft Transaction Server.

程序列表：
在开始菜单中，你会发现 Oracle 新安装的程序：

这些程序包括：

• Start and Stop Database are used to control the OracleServiceXE service
• Backup and Restore Database are scripts for backing up or restoring the database data using rman
• Run SQL Command Line opens a console based SQL*Plus which can be used to execute SQL commands or to run scripts against the database
• Get Started opens a web site used for investigating
  • storage, the amount of disk space used by tablespaces or drill to segments
  • current sessions and basic information about the sessions such as client and application information and active SQL statement
  • parameters show current initialization parameter values.

一些附加的工具

这是一个图形化的 SQL 编辑器，可用来执行 SQL 命令、查看结果集、创建各种数据库对象等等。