一：问题描述
备份控制文件时报错：
RMAN> restore controlfile from '/home/oracle/backup/PROD_32_20140829.bak';
Starting restore at 29-AUG-14
using channel ORA_DISK_1
RMAN-00571: ===========================================================
RMAN-00569: =============== ERROR MESSAGE STACK FOLLOWS ===============
RMAN-00571: ===========================================================
RMAN-03002: failure of restore command at 08/29/2014 02:41:21
RMAN-06496: must use the TO clause when the database is mounted or open
二：出错原因
在数据库mount状态下恢复了控制文件。
三：解决办法
在nomount状态下恢复控制文件。
四：示例
SQL> shutdown immediate;
ORA-01109: database not open
Database dismounted.
ORACLE instance shut down.
SQL> startup nomount;
ORACLE instance started.
Total System Global Area 285212672 bytes
Fixed Size 1218992 bytes
Variable Size 113247824 bytes
Database Buffers 167772160 bytes
Redo Buffers 2973696 bytes
没有再报错了。