alter databas/alter system/alter session命令区别

Use the ALTER SYSTEM statement to dynamically alter your Oracle Database instance. The settings stay in effect as long as the database is mounted.

 

Modifies a database, or the files and filegroups associated with the database. Adds or removes files and filegroups from a database, changes the attributes of a database or its files and filegroups, changes the database collation, and sets database options. Database snapshots cannot be modified

 

alter database 数据文件、表空间、日志文件等等,和物理上的文件有关系的一些变更,也就是对数据库的更改,一般改变的是物理上的,通过alter database操作时会触发controlfile header和其他一些物理文件头信息的变化
比如 :alter dtabase rename datafile


alter system     动态的改变实例的属性(参数),也就是对实例的更改,一般是逻辑上的
比如:alter system set db_cache_size 


alter session    改变的的是一个会话的属性
比如:alter session set nls_language

 

 

For further information see:

  • ALTER DATABASE
  • ALTER SYSTEM  

感谢:

http://www.itpub.net/viewthread.php?tid=1008132

http://topic.csdn.net/u/20080912/21/3f1c9b07-8a47-4377-8ca6-9fab01bafefd.html

让我搞清楚了这些概念~

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