从oracle 11.2.0.2.0开始，控制文件的快照文件必须能够被所有节点的数据实例访问到，并且必须放在共享的位置。否则，使用RMAN进行备份控制文件的时候会报如下错误：
ORA-00245: control file backup operation failed。
当使用备份脚本备份的时候，这个错误可能会导致备份工作中断。
公司同事也正好遇到这个问题。
METALINK 中的两篇文档：
RAC BACKUP FAILS WITH ORA-00245: CONTROL FILE BACKUP OPERATION FAILED [ID 1268725.1]
RMAN Snapshot Controlfile Must Reside on Shared Device for RAC database in 11G [ID 1263621.1]
解释并解决了此问题！摘要如下：
"RMAN creates a copy of the control file for read consistency, this is the snapshot controlfile. Due to the changes made to the controlfile backup mechanism in 11gR2 any instances in the cluster may write to the snapshot controlfile. Therefore, the snapshot controlfile file needs to be visible to all instances.
The same happens when a backup of the controlfile is created directly from sqlplus any instance in the cluster may write to the backup controfile file.
In 11gR2 onwards, the controlfile backup happens without holding the control file enqueue. For non-RAC database, this doesn't change anything.
But, for RAC database, the snapshot controlfile location must be in a shared file system that will be accessible from all the nodes."
当遇到此类问题时，警告日志文件会出现如下内容：
Alert log file content:
2011-08-20 00:11:53.650000 +02:00
Errors in file /opt/app/oracle/diag/rdbms/orcl/trace/cmsdb1_ora_15751.trc:
ORA-00245: control file backup operation failed
Trace File content:
Starting control autobackup
*** 2011-08-20 00:11:53.650
ORA-00245: control file backup operation failed
Got error: 245
Autobackup failed with following error
ORA-00245: control file backup operation failed
当前的控制文件配置：
rman target /
show all;
CONFIGURE SNAPSHOT CONTROLFILE NAME TO '/u01/app/oracle/product/11.2.0/db_1/dbs/snapcf_orcl.f'; # default
我们的环境中使用了asm，所以将控制文件备份到ASM中。
使用如下配置解决此问题：
rman target /
Recovery Manager: Release 11.2.0.2.0 - Production on Tue Aug 21 10:00:33 2011
Copyright (c) 1982, 2009, Oracle and/or its affiliates. All rights reserved.
connected to target database: CMSDB (DBID=1390673463)
RMAN> CONFIGURE SNAPSHOT CONTROLFILE NAME TO '+FLASH/SNCFORCL.ORA';
using target database control file instead of recovery catalog
new RMAN configuration parameters:
CONFIGURE SNAPSHOT CONTROLFILE NAME TO '+FLASH/SNCFORCL.ORA';
new RMAN configuration parameters are successfully stored
RMAN>
