改变归档模式到非归档模式:
1)SQL>SHUTDOWN IMMEDIATE;
2)SQL>STARTUP MOUNT;
3)SQL>ALTER DATABASE NOARCHIVELOG;
4)SQL>ALTER DATABASE OPEN;
在非归档模式下执行：
可以执行alter database datafile 。。这个
SQL> alter database datafile 4 offline drop;
Database altered.
然后在alter database open数据库，看看能否RMAN
SQL> alter database open;
Database altered.
执行RMAN报错：
RMAN> backup database;
Starting backup at 23-APR-14
using channel ORA_DISK_1
channel ORA_DISK_1: starting full datafile backupset
channel ORA_DISK_1: specifying datafile(s) in backupset
RMAN-03009: failure of backup command on ORA_DISK_1 channel at 04/23/2014 22:26:16
ORA-19602: cannot backup or copy active file in NOARCHIVELOG mode
continuing other job steps, job failed will not be re-run
channel ORA_DISK_1: starting full datafile backupset
channel ORA_DISK_1: specifying datafile(s) in backupset
including current control file in backupset
including current SPFILE in backupset
channel ORA_DISK_1: starting piece 1 at 23-APR-14
channel ORA_DISK_1: finished piece 1 at 23-APR-14
piece handle=/opt/flashbin/GFCDW/backupset/2014_04_23/o1_mf_ncsnf_TAG20140423T222615_9ohmd9mp_.bkp tag=TAG20140423T222615 comment=NONE
channel ORA_DISK_1: backup set complete, elapsed time: 00:00:03
RMAN-00571: ===========================================================
RMAN-00569: =============== ERROR MESSAGE STACK FOLLOWS ===============
RMAN-00571: ===========================================================
RMAN-03009: failure of backup command on ORA_DISK_1 channel at 04/23/2014 22:26:16
ORA-19602: cannot backup or copy active file in NOARCHIVELOG mode
现在改为MOUNT状态：可以备份成功的。
使用 RMAN 执行备份时：
如果目标数据库处于 NOARCHIVELOG 模式，则仅能执行“干净”表空间和数据文件备份（即“正常脱机”或“只读”表空间的备份）。
仅当数据库先完全关闭，然后在MOUNT 模式下重新启动时，才能执行数据库备份
备份数据库时：backup database;
归档模式mount还有open都可以
非归档只能mount
当数据库是Open状态时，采用的备份就叫做inconsistent backup了，即不一致的备份，这时你还得满足一个条件: 你的数据库必须得运行在归档模式。
原因 : 因为从一个不一致的备份进行restore,是需要做media recovery的，而media recovery又需要用到archived log。