Oracle基础--体系

1. 连接到Oralce

At the operating system prompt, enter the following command to start the SQL
Command Line and connect to the database:
CONN / AS SYSDBA
The slash (/) indicates that the database should authenticate you with operating
system authentication.

也可以用 conn username/passwd as sysdba

 system/manager

2. 启动Oracle和关闭Oracle

At the SQL Command Line prompt, enter the following command:

SQL> STARTUP

SQL> SHUTDOWN IMMEDIATE  // 如果shutdown失败，可以输入这个命令：SHUTDOWN ABORT. 之后可以重新启动和关闭oracle。

3. 数据库连接

  connect username/password@[//]host[:port][/service_name]

4. Oracle体系结构

　DATABASE：

The Oracle Database XE instance (which consists of the Oracle Database XE
background processes and allocated memory) works with a single database only.
Rather than enabling you to create multiple databases to accommodate different
applications, Oracle Database XE uses a single database, and accommodates multiple
applications by enabling you to separate data into different schemas.

　TABLESPACE：

There are various tablespaces, including the following:

1. Permanent tablespace　　2. Temporary tablespace　　3. Undo tablespace

 undo tablespace的目的：1） to undo any uncommitted changes.　　2)  to provide read consistency.　　3)  to support the flashback query feature.

tablespaces: 　　SYSTEM　　 SYSAUX　　TEMP　　UNDO　　USERS

 5. 用户和权限。

 默认用户：

　　sys 密码是 change_on_install　　// must connect to the database "AS SYSDBA."

　　system 密码是 manager