从Oracle11gR2 开始，在备份控制文件时，不在需要锁住controlfile enqueue。对于非RAC 的数据库， 没有任何改变，但对于RAC 数据

一．问题说明
操作系统： RedHat 5.8

数据库： 11.2.0.3

2节点RAC.

使用RMAN 备份的时候，报如下错误：

ORA-00245: control file backup failed;target is likely on a local file system

这个问题只存在Oracle 11gR2以后的RAC 环境。

二．ORA-245 触发条件
在以下的5种环境下，会出现ORA-00245的错误。

2.1 RAC 环境下，自动备份备份控制文件，，会因为ORA-245的错误而失败

Autobackup of controlfile in RMAN isfailing with error:
RMAN-571: ===========================================================
RMAN-569: =============== ERROR MESSAGE STACK FOLLOWS ===============
RMAN-571: ===========================================================
RMAN-3009: failure of Control File and SPFILE Autobackup command on
ORA_DISK_1 channel at 10/27/2010 12:13:31
ORA-245: control file backup operation failed

2.2 RAC 环境下，备份控制文件到非共享的本地路径，也会失败
SQL> ALTER DATABASE BACKUP CONTROLFILETO '/u01/backup/control.bk' REUSE
*
ERROR at line 1:
ORA-245: control file backup operation failed

2.3 在RAC 环境下，创建standby controlfile 到非共享的本地路径也会失败
SQL> alter database create standby controlfileas '/home/oracle/renostdbycntrl.ctl';

alter database create standby controlfileas
'/home/oracle/renostdbycntrl.ctl'
*
ERROR at line 1:
ORA-245: control file backup operation failed

2.4 在RAC 环境下，copy 当前的控制文件到本地路径
channel ch1: starting datafile copy
copying current control file
RMAN-571: ===========================================================
RMAN-569: =============== ERROR MESSAGE STACK FOLLOWS ===============
RMAN-571: ===========================================================
RMAN-3009: failure of backup command on 10/07/2011 11:36:42 channel at ch1
ORA-245: control file backup operation failed

2.5 RAC 环境下，controlfile 快照备份到非共享位置，RMAN 备份也会失败
RMAN-00571:========================================================
RMAN-00569: ============ ERROR MESSAGE STACK FOLLOWS =============
RMAN-00571: =========================================================
RMAN-03009: failure of resync command on default channel at 03/13/2012 10:19:41
ORA-00245: control file backup operation failed