Oracle可以运行在2种模式下:归档模式(archivelog)和非归档模式(noarchivelog),@H_301_2@归档模式可以提高Oracle数据库的可恢复性，生产数
@H_301_2@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。
@H_301_2@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。
@H_301_2@
@H_301_2@@H_301_2@1.管理员身份连接数据库
@H_301_2@
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
@H_301_2@2.查看当前归档模式，是归档还是非归档
@H_301_2@
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
> shutdown immediate;
Database closed.
Database dismounted.
ORACLE instance shut down.
> 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.
@H_301_2@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.
Database dismounted. ORACLE instance shut down. sqlDatabase mounted. sqldatabase noarchivelog; 230 sql>
