将配置恢复目录的保留策略，然后备份该恢复目录。 
1) 为 ORCL 数据库设置环境。 

[oracle@rtest ~]$ export ORACLE_SID=test0924

2) 启动 RMAN，在不指定目录的情况下使用恢复目录数据库作为目标。 

[oracle@rtest ~]$  rman target sys@rcat1028 

Recovery Manager: Release 11.2.0.3.0 - Production on Mon Oct 28 16:17:22 2013

Copyright (c) 1982, 2011, Oracle and/or its affiliates.  All rights reserved.

target database Password: ******                                                                                         
connected to target database: RCAT1028 (DBID=2744053659)

RMAN> 
3) 确保已将恢复目录的保留策略设置为冗余大于 1 。如果该值不大于 1 ，则至少将其设置为 2 。 

RMAN> show retention policy; 

using target database control file instead of recovery catalog
RMAN configuration parameters for database with db_unique_name RCAT1028 are:
CONFIGURE RETENTION POLICY TO REDUNDANCY 1; # default

RMAN> CONFIGURE RETENTION POLICY TO REDUNDANCY 2
2> ;

new RMAN configuration parameters:
CONFIGURE RETENTION POLICY TO REDUNDANCY 2;
new RMAN configuration parameters are successfully stored

4) 尝试备份数据库。 
RMAN> backup database;

Starting backup at 28-OCT-13
allocated channel: ORA_DISK_1
channel ORA_DISK_1: SID=190 device type=DISK
channel ORA_DISK_1: starting full datafile backup set
channel ORA_DISK_1: specifying datafile(s) in backup set
RMAN-03009: failure of backup command on ORA_DISK_1 channel at 10/28/2013 16:18:54
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 backup set
channel ORA_DISK_1: specifying datafile(s) in backup set
including current control file in backup set
including current SPFILE in backup set
channel ORA_DISK_1: starting piece 1 at 28-OCT-13
channel ORA_DISK_1: finished piece 1 at 28-OCT-13
piece handle=+RECOVERY/rcat1028/backupset/2013_10_28/ncsnf0_tag20131028t161854_0.261.830017137 tag=TAG20131028T161854 comment=NONE
channel ORA_DISK_1: backup set complete, elapsed time: 00:00:04
RMAN-00571: ===========================================================
RMAN-00569: =============== ERROR MESSAGE STACK FOLLOWS ===============
RMAN-00571: ===========================================================

RMAN-03009: failure of backup command on ORA_DISK_1 channel at 10/28/2013 16:18:54
ORA-19602: cannot backup or copy active file in NOARCHIVELOG mode

 
 
RMAN> 

请注意，无法备份模式不为 ARCHIVELOG  的打开数据库。为确保最高的可用性，恢复目录数据库应以 ARCHIVELOG  模式运行。
 
5) 退出 RMAN。 

RMAN>  exit 

6) 首先设置 RCAT1028数据库的环境，然后将恢复目录数据库更改为在 ARCHIVELOG  模式下运行。 
[oracle@rtest dbs]$ export ORACLE_SID=rcat1028
[oracle@rtest dbs]$ sqlplus /nolog

SQL*Plus: Release 11.2.0.3.0 Production on Mon Oct 28 16:21:36 2013

Copyright (c) 1982, 2011, Oracle.  All rights reserved.

SQL> conn /as sysdba
Connected.
SQL> shutdown immediate;
Database closed.
Database dismounted.
ORACLE instance shut down.
SQL> startup mount
ORACLE instance started.

Total System Global Area 1235959808 bytes
Fixed Size                  2227904 bytes
Variable Size             738197824 bytes
Database Buffers          486539264 bytes
Redo Buffers                8994816 bytes
Database mounted.
SQL> alter database archivelog;

Database altered.

SQL> alter database open;

Database altered.

SQL> archive log list;
Database log mode              Archive Mode
Automatic archival             Enabled
Archive destination            USE_DB_RECOVERY_FILE_DEST
Oldest online log sequence     3
Next log sequence to archive   5
Current log sequence           5
SQL> 
7) 确认RCAT1028数据库环境， 按照前面提供的步骤重新登录 RMAN。 

[oracle@rtest ~]$ export ORACLE_SID=test0924
[oracle@rtest ~]$ rman target sys@rcat1028

Recovery Manager: Release 11.2.0.3.0 - Production on Mon Oct 28 16:25:17 2013

Copyright (c) 1982, 2011, Oracle and/or its affiliates.  All rights reserved.

target database Password: ******                                                                                         
connected to target database: RCAT1028 (DBID=2744053659)

RMAN> 

9) 备份恢复目录数据库。此时操作应成功。 

RMAN> backup database;

Starting backup at 28-OCT-13
using target database control file instead of recovery catalog
allocated channel: ORA_DISK_1
channel ORA_DISK_1: SID=131 device type=DISK
channel ORA_DISK_1: starting full datafile backup set
channel ORA_DISK_1: specifying datafile(s) in backup set
input datafile file number=00001 name=+DATA/rcat1028/datafile/system.262.830015445
input datafile file number=00002 name=+DATA/rcat1028/datafile/sysaux.261.830015451
input datafile file number=00003 name=+DATA/rcat1028/datafile/undotbs1.265.830015451
input datafile file number=00005 name=+DATA/rcat01.dbf
input datafile file number=00004 name=+DATA/rcat1028/datafile/users.259.830015453
channel ORA_DISK_1: starting piece 1 at 28-OCT-13
channel ORA_DISK_1: finished piece 1 at 28-OCT-13
piece handle=+RECOVERY/rcat1028/backupset/2013_10_28/nnndf0_tag20131028t162544_0.262.830017545 tag=TAG20131028T162544 comment=NONE
channel ORA_DISK_1: backup set complete, elapsed time: 00:03:25
channel ORA_DISK_1: starting full datafile backup set
channel ORA_DISK_1: specifying datafile(s) in backup set
including current control file in backup set
including current SPFILE in backup set
channel ORA_DISK_1: starting piece 1 at 28-OCT-13
channel ORA_DISK_1: finished piece 1 at 28-OCT-13
piece handle=+RECOVERY/rcat1028/backupset/2013_10_28/ncsnf0_tag20131028t162544_0.263.830017753 tag=TAG20131028T162544 comment=NONE
channel ORA_DISK_1: backup set complete, elapsed time: 00:00:04
Finished backup at 28-OCT-13

RMAN> exit


Recovery Manager complete.
[oracle@rtest ~]$