最近在数据库恢复中遇到一个案例：xx单位1.5T oracle 10.2.0.4(redhat 4.5)，因为异常关闭操作系统，导致数据库不能启动，需要帮忙恢复。该数据库为非归档模式，使用裸设备,一个裸设备文件大小(35G)，数据库文件大小4-30G都有，现在客户要求我们不能对现有环境进行任何操作，需要克隆一份数据库出来，然后在克隆的库上进行数据库恢复操作.数据库环境的克隆最好的方法就是使用rman来完成,但是该数据库为非归档模式,无法直接使用rman进行备份操作.最后采取dd的方式处理(需要注意dd文件大小为block_size*(v$datafile.blocks+1)+v$datafile.offset).因为不能使用rman的一条命令处理,心里一直不舒服,在家里实验,终于还是确定可以通过重建控制文件的方法来欺骗rman是归档模式,来实现rman完成类似工作.
数据库非非归档模式

SQL> select * from v$version;
BANNER
--------------------------------------------------------------------------------
Oracle Database 11g Enterprise Edition Release 11.2.0.3.0 - Production
PL/SQL Release 11.2.0.3.0 - Production
CORE    11.2.0.3.0      Production
TNS for Linux: Version 11.2.0.3.0 - Production
NLSRTL Version 11.2.0.3.0 - Production
SQL> archive log list;
Database log mode              No Archive Mode
Automatic archival             Disabled
Archive destination            /u01/oracle/oradata/ora11g/archivelog
Oldest online log sequence     7
Current log sequence           9

非归档模式尝试rman 备份

RMAN> backup database format '/u01/oracle/oradata/orall1g_%U';
Starting backup at 22-JAN-13
using target database control file instead of recovery catalog
allocated channel: ORA_DISK_1
channel ORA_DISK_1: SID=10 device type=DISK
channel ORA_DISK_1: starting full datafile backup set
channel ORA_DISK_1: specifying datafile(s) in backup set
RMAN-03009: failure of backup command on ORA_DISK_1 channel at 01/22/2013 16:10:49
ORA-19602: cannot backup or copy active file in NOARCHIVELOG mode
continuing other job steps, job failed will not be re-run
channel ORA_DISK_1: starting full datafile backup set
channel ORA_DISK_1: specifying datafile(s) in backup set
including current control file in backup set
including current SPFILE in backup set
channel ORA_DISK_1: starting piece 1 at 22-JAN-13
channel ORA_DISK_1: finished piece 1 at 22-JAN-13
piece handle=/u01/oracle/oradata/orall1g_13o02k8a_1_1 tag=TAG20130122T161048 comment=NONE
channel ORA_DISK_1: backup set complete, elapsed time: 00:00:03
RMAN-00571: ===========================================================
RMAN-00569: =============== ERROR MESSAGE STACK FOLLOWS ===============
RMAN-00571: ===========================================================

rman的backup or copy命令不能在非归档模式下执行

尝试修改数据库为归档模式

SQL> alter database archivelog;
alter database archivelog
*
ERROR at line 1:
ORA-00265: instance recovery required, cannot set ARCHIVELOG mode

数据库非正常关闭,不能修改归档模式

重建控制文件

SQL> alter database backup controlfile to trace as '/tmp/ctl';
Database altered.
SQL> shutdown immediate
ORA-01109: database not open
Database dismounted.
ORACLE instance shut down.
--备份当前控制文件(保留控制文件现场)
SQL> STARTUP NOMOUNT
ORACLE instance started.
Total System Global Area  313860096 bytes
Fixed Size                  1344652 bytes
Variable Size             285215604 bytes
Database Buffers           20971520 bytes
Redo Buffers                6328320 bytes
SQL> CREATE CONTROLFILE REUSE DATABASE "ORA11G" NORESETLOGS  ARCHIVELOG
  2      MAXLOGFILES 16
  3      MAXLOGMEMBERS 3
  4      MAXDATAFILES 100
  5      MAXINSTANCES 8
  6      MAXLOGHISTORY 292
  7  LOGFILE
  8    GROUP 1 '/u01/oracle/oradata/ora11g/redo01.log'  SIZE 50M BLOCKSIZE 512,
  9    GROUP 2 '/u01/oracle/oradata/ora11g/redo02.log'  SIZE 50M BLOCKSIZE 512,
 10    GROUP 3 '/u01/oracle/oradata/ora11g/redo03.log'  SIZE 50M BLOCKSIZE 512
 11  DATAFILE
 12    '/u01/oracle/oradata/ora11g/system01.dbf',
 13    '/u01/oracle/oradata/ora11g/sysaux01.dbf',
 14    '/u01/oracle/oradata/ora11g/users01.dbf',
 15    '/u01/oracle/oradata/ora11g/dbfs01.dbf',
 16    '/u01/oracle/oradata/ora11g/tts_xifenfei02.dbf',
 17    '/u01/oracle/oradata/ora11g/tts_xifenfei01.dbf',
 18    '/u01/oracle/oradata/ora11g/system02.dbf',
 19    '/u01/oracle/oradata/ora11g/czum01.dbf',
 20    '/u01/oracle/oradata/ora11g/undotbs02.dbf'
 21  CHARACTER SET ZHS16GBK
 22  ;
Control file created.

数据库已经变为归档模式

SQL> archive log list;
Database log mode              Archive Mode
Automatic archival             Disabled
Archive destination            /u01/oracle/oradata/ora11g/archivelog
Oldest online log sequence     7
Next log sequence to archive   7
Current log sequence           9

归档模式尝试rman备份

RMAN> backup datafile 1 format '/u01/oracle/oradata/system01_%U';
Starting backup at 22-JAN-13
using channel ORA_DISK_1
channel ORA_DISK_1: starting full datafile backup set
channel ORA_DISK_1: specifying datafile(s) in backup set
input datafile file number=00001 name=/u01/oracle/oradata/ora11g/system01.dbf
channel ORA_DISK_1: starting piece 1 at 22-JAN-13
channel ORA_DISK_1: finished piece 1 at 22-JAN-13
piece handle=/u01/oracle/oradata/system01_02o02kl7_1_1 tag=TAG20130122T161742 comment=NONE
channel ORA_DISK_1: backup set complete, elapsed time: 00:01:15
Finished backup at 22-JAN-13
RMAN-06497: WARNING: control file is not current, control file AUTOBACKUP skipped

因为现在的控制文件是新创建的，不能算是数据库的当前控制文件,所以未被rman自动备份(很好理解，重建控制文件后，我们做恢复都要使用using backup controlfile命令)

总结说明
1.数据库为非归档模式,不能使用rman的backup和copy命令来备份
2.因为数据库为非正常关闭不能直接修改为归档模式
3.通过重建控制文件修改数据库(注意备份)为归档模式实现rman正常备份
4.当rman备份好之后，使用原先控制文件替换现在控制文件