在部署完active data guard后，不但可以将只读的查询交给备库执行，还可以把日常的数据库备份工作放在备库上执行，从而减轻主库的压力，充分的发挥服务器资源，下面演示下利用备库备份来还原主库数据的过程！
一：主库上创建表空间，并在表空间上建表，插入测试数据，同时检查备库的同步情况
SQL> create tablespace test01 datafile '/u01/app/Oracle/oradata/db1/test01.dbf' size 10M;
Tablespace created.
SQL> create table rman tablespace test01 as select object_id,object_name from dba_objects;
Table created.
SQL> select count(*) from rman;
COUNT(*)
----------
76379
[oracle@db2 db1]$ sqlplus /nolog
SQL*Plus: Release 11.2.0.3.0 Production on Mon Oct 29 11:37:38 2012
Copyright (c) 1982, 2011, Oracle. All rights reserved.
SQL> conn /as sysdba
Connected.
SQL> select count(*) from rman;
COUNT(*)
----------
76379
二：在备库上使用rman对新建的表空间test01进行备份
[oracle@db2 db1]$ rman target /
Recovery Manager: Release 11.2.0.3.0 - Production on Mon Oct 29 11:38:01 2012
Copyright (c) 1982, 2011, Oracle and/or its affiliates. All rights reserved.
connected to target database: DB1 (DBID=1387827106)
RMAN> report schema;
RMAN> backup tablespace test01 format '/home/oracle/test01_%U';
Starting backup at 2012-10-29-11:38:50
allocated channel: ORA_DISK_1
channel ORA_DISK_1: SID=1 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=00034 name=/u01/app/oracle/oradata/db1/test01.dbf
channel ORA_DISK_1: starting piece 1 at 2012-10-29-11:38:51
channel ORA_DISK_1: finished piece 1 at 2012-10-29-11:38:52
piece handle=/home/oracle/test01_03novc2b_1_1 tag=TAG20121029T113851 comment=NONE
channel ORA_DISK_1: backup set complete, elapsed time: 00:00:01
Finished backup at 2012-10-29-11:38:52
三：关闭主库后删除表空间数据文件，模拟数据丢失场景
[oracle@db1 ~]$ sqlplus /nolog
SQL*Plus: Release 11.2.0.3.0 Production on Mon Oct 29 11:39:49 2012
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> exit
[oracle@db1 ~]$ rm -rf /u01/app/oracle/oradata/db1/test01.dbf
四：重新启动主库，只能启动到mount状态
[oracle@db1 ~]$ sqlplus /nolog
SQL*Plus: Release 11.2.0.3.0 Production on Mon Oct 29 11:41:42 2012
Copyright (c) 1982, 2011, Oracle. All rights reserved.
SQL> conn /as sysdba
Connected to an idle instance.
SQL> startup
ORACLE instance started.
Total System Global Area 1536602112 bytes
Fixed Size 2228624 bytes
Variable Size 1174408816 bytes
Database Buffers 352321536 bytes
Redo Buffers 7643136 bytes
Database mounted.
ORA-01157: cannot identify/lock data file 34 - see DBWR trace file
ORA-01110: data file 34: '/u01/app/oracle/oradata/db1/test01.dbf'
SQL> select open_mode,database_role from v$database;
OPEN_MODE DATABASE_ROLE
-------------------- ----------------
MOUNTED PRIMARY
