事由如下：
   不记如何把以前作的控制文件备份（主库上），手工删除，导致 利用rman恢复总提示如下错误：
-bash-3.1$ rman target sys/system@centos auxiliary sys/system

Recovery Manager: Release 10.2.0.4.0 - Production on Sun Jan 31 02:45:07 2010

Copyright (c) 1982, 2007, Oracle.  All rights reserved.

connected to target database: CENTOS (DBID=3005679176)
connected to auxiliary database: CENTOS (not mounted)

RMAN> run
2> {set until scn 671285;
3> duplicate target database for standby
4> nofilenamecheck
5> dorecover;
6> }

executing command: SET until clause
using target database control file instead of recovery catalog

Starting Duplicate Db at 31-JAN-10
allocated channel: ORA_AUX_DISK_1
channel ORA_AUX_DISK_1: sid=159 devtype=DISK

contents of Memory Script.:
{
   set until scn  671285;
   restore clone standby controlfile;
   sql clone 'alter database mount standby database';
}
executing Memory Script

executing command: SET until clause

Starting restore at 31-JAN-10
using channel ORA_AUX_DISK_1

channel ORA_AUX_DISK_1: starting datafile backupset restore
channel ORA_AUX_DISK_1: restoring control file
channel ORA_AUX_DISK_1: reading from backup piece /oracle/rmanbak/CENTOS_standbyctl.bak
ORA-19870: error reading backup piece /oracle/rmanbak/CENTOS_standbyctl.bak
ORA-19505: failed to identify file "/oracle/rmanbak/CENTOS_standbyctl.bak"
ORA-27037: unable to obtain file status
Linux Error: 2: No such file or directory
Additional information: 3
failover to previous backup


然后在主库进入rman操作如下
rman target sys/system@centos
 1,先验证主库备份的有效性
     restore database validate;
     restore archivelog all validate;
 2,list backup of database;
    list copy of database;
    list backupset of database;
    ....同理（对于其它备份对象）
    list backup of controlfile;
    list backup of archivelog;
   
    crosscheck backup of controlfile;--这下子就出来好多无效的控制文件备份

   哈哈，下来你就可以用delete真正把这些东东，从rman的控制文件中清除，下次rman在恢复就会再用这些信息了，以免给你添麻烦
    delete noprompt obsolete;