经过思考，笔者提出了一种假说。如果Control File在Standby端是不允许进行修改，但是在Primary端允许修改的话。可否进行一次有准备的Switchover动作，让Standby端临时性变为可以修改的Control File。修改之后再Switchover就可以了。
实验过程如下，首先在主库上进行角色切换动作。
SQL> select open_mode, database_role from v$database;
OPEN_MODE DATABASE_ROLE
-------------------- ----------------
READ WRITE PRIMARY
SQL> alter database commit to switchover to standby with session shutdown;
Database altered.
SQL> quit
Disconnected from Oracle Database 11g Enterprise Edition Release 11.2.0.4.0 - 64bit Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options
[oracle@vLIFE-URE-OT-DB-PRIMARY ~]$ ps -ef | grep pmon
oracle 30720 30659 0 10:40 pts/0 00:00:00 grep pmon
主库切换之后，自动停机。下面进行备库操作。
[oracle@vLIFE-URE-OT-DB-STANDBY ~]$ sqlplus /nolog
SQL*Plus: Release 11.2.0.4.0 Production on Wed Jan 13 10:38:32 2016
Copyright (c) 1982, 2013, Oracle. All rights reserved.
SQL> conn / as sysdba
Connected.
SQL> select open_mode, database_role from v$database;
OPEN_MODE DATABASE_ROLE
-------------------- ----------------
READ ONLY WITH APPLY PHYSICAL STANDBY
SQL> select switchover_status from v$database;
SWITCHOVER_STATUS
--------------------
TO PRIMARY
SQL> alter database commit to switchover to primary with session shutdown;
Database altered.
SQL> select open_mode, database_role from v$database;
OPEN_MODE DATABASE_ROLE
-------------------- ----------------
MOUNTED PRIMARY
SQL> alter database open;
Database altered.
原来的主库（先备库）启动，进行Redo Apply过程。
[oracle@vLIFE-URE-OT-DB-PRIMARY ~]$ sqlplus /nolog
SQL*Plus: Release 11.2.0.4.0 Production on Wed Jan 13 10:42:37 2016
Copyright (c) 1982, 2013, Oracle. All rights reserved.
SQL> conn / as sysdba
Connected to an idle instance.
SQL> startup mount;
ORACLE instance started.
Total System Global Area 2471931904 bytes
Fixed Size 2255752 bytes
Variable Size 738198648 bytes
Database Buffers 1711276032 bytes
Redo Buffers 20201472 bytes
Database mounted.
SQL> alter database recover managed standby database using current logfile disconnect;
Database altered.
--日志传输正常。
SQL> select STATUS from v$archive_dest_status;
STATUS
---------
VALID
VALID
INACTIVE
修改原备库RMAN项目。
[oracle@vLIFE-URE-OT-DB-STANDBY trace]$ rman nocatalog
Recovery Manager: Release 11.2.0.4.0 - Production on Wed Jan 13 10:48:47 2016
Copyright (c) 1982, 2011, Oracle and/or its affiliates. All rights reserved.
RMAN> connect target /
connected to target database: VLIFE (DBID=4207470439)
using target database control file instead of recovery catalog
RMAN> show all;
RMAN configuration parameters for database with db_unique_name VLIFESB are:
CONFIGURE RETENTION POLICY TO REDUNDANCY 1; # default
CONFIGURE BACKUP OPTIMIZATION ON;
RMAN> configure retention policy to recovery window of 15 days;
new RMAN configuration parameters:
CONFIGURE RETENTION POLICY TO RECOVERY WINDOW OF 15 DAYS;
new RMAN configuration parameters are successfully stored
RMAN> show all;
RMAN configuration parameters for database with db_unique_name VLIFESB are:
CONFIGURE RETENTION POLICY TO RECOVERY WINDOW OF 15 DAYS;
CONFIGURE BACKUP OPTIMIZATION ON;
CONFIGURE DEFAULT DEVICE TYPE TO DISK; # default
下面就可以使用相同的方法将原来的Primary和Standby关系切换回来。由于篇幅所限，不进行详细说明。操作后，修改的参数生效。
[oracle@vLIFE-URE-OT-DB-STANDBY trace]$ rman nocatalog
Recovery Manager: Release 11.2.0.4.0 - Production on Wed Jan 13 11:11:18 2016
Copyright (c) 1982, 2011, Oracle and/or its affiliates. All rights reserved.
RMAN> connect target /
connected to target database: VLIFE (DBID=4207470439)
using target database control file instead of recovery catalog
RMAN> show all;
RMAN configuration parameters for database with db_unique_name VLIFESB are:
CONFIGURE RETENTION POLICY TO RECOVERY WINDOW OF 15 DAYS;
CONFIGURE BACKUP OPTIMIZATION ON;
3、结论