Oracle可以运行在2种模式下:归档模式(archivelog)和非归档模式(noarchivelog),归档模式可以提高Oracle数据库的可恢复性，生产数

据库都应该运行在此模式下，归档模式应该和相应的备份策略相结合，只有归档模式没有相应的备份策略只会带来麻烦。

非归档，没归档日志，基本上没办法恢复，非归档下，RMAN只以冷备不能热备。数据重要，最好打开归档模式。归档模式可以将数据恢复到任意一个时刻。

1.管理员身份连接数据库

C:\Users\Administrator>sqlplus sys/sys@prjdb as sysdba

sql*Plus: Release 11.2.0.1.0 Production on Tue Jun 17 23:50:55 2014

Copyright (c) 1982,2010,Oracle.  All rights reserved.


Connected to:
Oracle Database 11g Enterprise Edition Release 0 - 64bit Production
With the Partitioning,OLAP,Data Mining and Real Application Testing options

2.查看当前归档模式，是归档还是非归档

sql> archive log list;
Database log mode              No Archive Mode
Automatic archival             Disabled
Archive destination            USE_DB_RECOVERY_FILE_DEST
Oldest online log sequence     228
Current log sequence           230

3.关闭数据库

> shutdown immediate; Database closed. Database dismounted. ORACLE instance shut down.

4.启动数据库到mount状态

> startup mount; ORACLE instance started. Total System Global Area 3423965184 bytes Fixed Size 2180544 bytes Variable Size 2013268544 bytes Database Buffers 1392508928 bytes Redo Buffers 16007168 bytes Database mounted.

5.启动归模式

alter database archivelog; Database altered. sqllog mode Archive Mode Automatic archival Enabled Archive destination USE_DB_RECOVERY_FILE_DEST Oldest online Next log sequence to archive 230 6.启动数据库

database open; Database altered.

7.关闭归档模式（与上面大同小异）

Database dismounted. ORACLE instance shut down. sqlDatabase mounted. sqldatabase noarchivelog; 230 sql>