在刚刚接手Oracle时，这个问题困扰了我一段时间，现在将问题的解决过程分享一下

Oracle版本：11gR2

OS环境：Centos6.4

问题重现：

1. 接手数据库是写了一个备份脚本，脚本内容如下：

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# !/bin/bash
# Name: rmanbk_level0.sh
# Write by: Datura at 2014/11/11 v1.0
# Description: The script is used to make the zero level backup for the orcl Library

# The definition of the variable
lock_file=/tmp/rmanbk.lock
oracleid=`cat /etc/passwd|grep oracle|awk -F: '{print $3}'`

# Check the script to run or not
if [ -f $lock_file ];then
        pid=`cat $lock_file`
        ps $pid &> /dev/null
        [ $? -eq 0 ] && echo "Script is running..." && exit 1
fi

# Create process lock
echo $$ > $lock_file

# Only allows the oracle to run
[ $UID -ne $oracleid ] && echo "Please run as oracle !!" && exit 4

# To set environment variables
export ORACLE_BASE=/u01/app/oracle
export ORACLE_HOME=$ORACLE_BASE/product/11.2.0/db_1
export PATH=$ORACLE_HOME/bin:$PATH
export ORACLE_SID=orcl1
export NLS_LANG=AMERICAN_AMERICA.AL32UTF8

echo on
rman target /  msglog=/storage/script/log/rmanbk_level0_`date +%Y'-'%m'-'%d'-'%H':'%M':'%S`.log <RUN {
allocate channel c1 type disk;
allocate channel c2 type disk;
allocate channel c3 type disk;
allocate channel c4 type disk;
backup as compressed backupset incremental level 0 database format '/storage/arch/rman/rmanbk_level0_%d_%I_%s_%p_%T.bkp';
crosscheck archivelog all;
backup archivelog all format '/storage/arch/rman/rmanbk_archivelog_%d_%I_%s_%p_%T.bkp';
crosscheck backup;
delete noprompt obsolete;
delete noprompt expired backupset;
release channel c1;
release channel c2;
release channel c3;
release channel c4;
}
exit
EOF
echo off

find /storage/arch/rman/ -mtime -0.5 -type f -exec zip /storage/arch/rman/rmanbk_level0`date +%F`.zip {} \;
scp /storage/arch/rman/rmanbk_level0`date +%F`.zip backup.demon.com:/home/oracle/orabackup
rm -rf /storage/arch/rman/rmanbk_level0`date +%F`.zip
find /storage/script/log -mtime +7 -exec rm -rf {} \;

2. 有一天在备份日志里出现了下面的报错信息

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RMAN-06207: WARNING: 1 objects could not be deleted for DISK channel(s) due
RMAN-06208:          to mismatched status.  Use CROSSCHECK command to fix status
RMAN-06210: List of Mismatched objects
RMAN-06211: =========================================================
RMAN-06212:   Object Type   Filename/Handle
RMAN-06213: --------------- ---------------------------------------------------
RMAN-06214: Datafile Copy   +DATA/orcl/snapc_orcl.f

3. 报错信息处理过程

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RMAN> crosscheck backupset;

RMAN> report obsolete;

RMAN retention policy will be applied to the command
RMAN retention policy is set to recovery window of 2 days
Report of obsolete backups and copies
Type                 Key    Completion Time    Filename/Handle
-------------------- ------ ------------------ --------------------
Control File Copy     5      12-DEC-14          +DATA/orcl/snapc_orcl.f

RMAN> delete noprompt obsolete;

RMAN-00571: ====================================================
RMAN-00569: ===============ERROR MESSAGE STACK FOLLOWS ===============
RMAN-00571: ====================================================
RMAN-03009: failure of delete command on c2 channel at 11/20/2014 09:03:14
ORA-19606: Cannot copy or restore to snapshot control file

RMAN> show snapshot controlfile name;

RMAN configuration parameters for database with db_unique_name ORCL are:
CONFIGURE SNAPSHOT CONTROLFILE NAME TO '/u01/app/oracle/product/11.2.0/db_1/dbs/snapcf_orcl1.f'; # default

RMAN> configure snapshot controlfile name to '/u01/app/oracle/product/11.2.0/db_1/dbs/snapcf_orcl1.f_bak';

new RMAN configuration parameters:
CONFIGURE SNAPSHOT CONTROLFILE NAME TO '/u01/app/oracle/product/11.2.0/db_1/dbs/snapcf_orcl1.f_bak';
new RMAN configuration parameters are successfully stored

RMAN> crosscheck controlfilecopy  '/u01/app/oracle/product/11.2.0/db_1/dbs/snapcf_orcl1.f';

released channel: ORA_DISK_1
allocated channel: ORA_DISK_1
channel ORA_DISK_1: SID=80 instance=orcl1 device type=DISK
validation failed for control file copy
control file copy file name=/u01/app/oracle/product/11.2.0/db_1/dbs/snapcf_orcl1.f RECID=2 STAMP=863884566
Crosschecked 1 objects

RMAN> delete expired controlfilecopy '/u01/app/oracle/product/11.2.0/db_1/dbs/snapcf_orcl1.f';

released channel: ORA_DISK_1
allocated channel: ORA_DISK_1
channel ORA_DISK_1: SID=80 instance=orcl1 device type=DISK
List of Control File Copies
=========================================================================================
Key     S Completion Time Ckp SCN    Ckp Time
------- - --------------- ---------- ---------------
2       X 17-NOV-14       67553950   17-NOV-14
        Name: /u01/app/oracle/product/11.2.0/db_1/dbs/snapcf_orcl1.f
        Tag: TAG20141117T155602

Do you really want to delete the above objects (enter YES or NO)? yes
deleted control file copy
control file copy file name=/u01/app/oracle/product/11.2.0/db_1/dbs/snapcf_orcl1.f RECID=2 STAMP=863884566
Deleted 1 EXPIRED objects

RMAN> configure snapshot controlfile name to '/u01/app/oracle/product/11.2.0/db_1/dbs/snapcf_orcl1.f';

old RMAN configuration parameters:
CONFIGURE SNAPSHOT CONTROLFILE NAME TO '/u01/app/oracle/product/11.2.0/db_1/dbs/snapcf_orcl1.f_bak';
new RMAN configuration parameters:
CONFIGURE SNAPSHOT CONTROLFILE NAME TO '/u01/app/oracle/product/11.2.0/db_1/dbs/snapcf_orcl1.f';
new RMAN configuration parameters are successfully stored

RMAN> configure snapshot controlfile name clear;

old RMAN configuration parameters:
CONFIGURE SNAPSHOT CONTROLFILE NAME TO '/u01/app/oracle/product/11.2.0/db_1/dbs/snapcf_orcl1.f';
RMAN configuration parameters are successfully reset to default value

4. 通过上面的常规操作暂时解决了问题，但没几天就会再次出现相同的问题

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RMAN-00571: ==========================================================
RMAN-00569: ================= ERROR MESSAGE STACK FOLLOWS ===================
RMAN-00571: ==========================================================
RMAN-03009: failure of Control File and SPFILE Autobackup command on c1 channel at 12/12/2014 01:05:19
ORA-00245: control file backup failed; target is likely on a local file system

5. 上面的常规操作只能暂时解决问题，不能解决根本问题，于是翻阅官方文档得到以下信息

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从11gR2开始，在备份控制文件时不再需要锁住controlfile enqueue
对于非RAC环境的数据库没有任何的改变
但是对于RAC环境，因为控制文件备份机制的改变
集群中的所有节点都必须能够访问快照控制文件，所以快照控制文件要对所有实例可见
如果快照控制文件没有放到共享设备上，当rman备份快照控制文件时就会出现以上的错误

6. 根据得到的信息做出如下调整

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RMAN> show snapshot controlfile name;

RMAN> configure snapshot controlfile name to '/storage/snap_control/snapcf_%d_%I_%s_%p_%T.f';

RMAN> configure snapshot controlfile name to '+DATA/orcl/snapcf_orcl.f';   --也可以指定到对应的ASM磁盘组（磁盘组不支持通配符命名）

将控制文件快照放到共享存储之后就没有再出现上面的错误了

在出现问题时我们都习惯用自己的经验采用常规的手法去解决问题

但有时候翻阅官档是个不错的选择

虽然官档不能告诉你具体的操作步骤

却可以给予解决根本问题的正确指引

-------------------------------------------------------以上为个人观点阐述，如有不妥，欢迎指点-----------------------------------------------------------------------