1、Use the CONFIGURE CONTROLFILE AUTOBACKUP command to eanable
设置RMAN配置文件，将CONFIGE CONTROLFILE AUTOBACKUP 为ON状态，可以是实现控制文件的备份。如果CONFIGURE CONTROLFILE AUTOBACKUP 为OFF,那么在备份system表空间的时候，也会备份congrol file。
2、when enabled,RMAN automatically performs a back up of the control file and current server parameter file after BACKUP or COPY commands.
3、Back ups also occur after structural changes to the database .
4、Backup is given a default name.
备份Controlfile与system parameter file的方法
（一）、设置如下配置参数，实现controlfile与system parameter file的备份
RMAN> show all;RMAN configuration parameters for database with db_unique_name POLI are:CONFIGURE RETENTION POLICY TO REDUNDANCY 1; # defaultCONFIGURE BACKUP OPTIMIZATION OFF; # defaultCONFIGURE DEFAULT DEVICE TYPE TO DISK; # defaultCONFIGURE CONTROLFILE AUTOBACKUP ON;CONFIGURE CONTROLFILE AUTOBACKUP FORMAT FOR DEVICE TYPE DISK TO '%F'; # defaultCONFIGURE DEVICE TYPE DISK PARALLELISM 1 BACKUP TYPE TO BACKUPSET; # defaultCONFIGURE DATAFILE BACKUP COPIES FOR DEVICE TYPE DISK TO 1; # defaultCONFIGURE ARCHIVELOG BACKUP COPIES FOR DEVICE TYPE DISK TO 1; # defaultCONFIGURE MAXSETSIZE TO UNLIMITED; # defaultCONFIGURE ENCRYPTION FOR DATABASE OFF; # defaultCONFIGURE ENCRYPTION ALGORITHM 'AES128'; # defaultCONFIGURE COMPRESSION ALGORITHM 'BASIC' AS OF RELEASE 'DEFAULT' OPTIMIZE FOR LOAD TRUE ; # defaultCONFIGURE ARCHIVELOG DELETION POLICY TO NONE; # defaultCONFIGURE SNAPSHOT CONTROLFILE NAME TO '/u01/oracle/dbs/snapcf_poli.f'; # default
（二）、执行命令backup current controlfile，实现controlfile与spfile的备份;(单独执行controlfile与spfile的命令)
RMAN> backup current controlfile;Starting backup at 23-MAR-13using channel ORA_DISK_1channel ORA_DISK_1: starting full datafile backup setchannel ORA_DISK_1: specifying datafile(s) in backup setincluding current control file in backup setchannel ORA_DISK_1: starting piece 1 at 23-MAR-13channel ORA_DISK_1: finished piece 1 at 23-MAR-13piece handle=/u01/flash_recovery_area/POLI/backupset/_03_23/o1_mf_ncnnf_TAG0323T234359_8nvmg18j_.bkp tag=TAG0323T234359 comment=NONEchannel ORA_DISK_1: backup set complete, elapsed time: 00:00:03Finished backup at 23-MAR-13Starting Control File Autobackup at 23-MAR-13piece handle=/u01/flash_recovery_area/POLI/autobackup/_03_23/o1_mf_n_810863044_8nvmg4dv_.bkp comment=NONEFinished Control File Autobackup at 23-MAR-13
（三）、使用include子句，实现control file的备份
RMAN> backup datafile 4 include current controlfile;Starting backup at 23-MAR-13using channel ORA_DISK_1channel ORA_DISK_1: starting full datafile backup setchannel ORA_DISK_1: specifying datafile(s) in backup setinput datafile file number=00004 name=/u01/oradata/poli/users01.dbfchannel ORA_DISK_1: starting piece 1 at 23-MAR-13channel ORA_DISK_1: finished piece 1 at 23-MAR-13piece handle=/u01/flash_recovery_area/POLI/backupset/_03_23/o1_mf_nnndf_TAG0323T234751_8nvmo843_.bkp tag=TAG0323T234751 comment=NONEchannel ORA_DISK_1: backup set complete, elapsed time: 00:00:03channel ORA_DISK_1: starting full datafile backup setchannel ORA_DISK_1: specifying datafile(s) in backup setincluding current control file in backup setchannel ORA_DISK_1: starting piece 1 at 23-MAR-13channel ORA_DISK_1: finished piece 1 at 23-MAR-13piece handle=/u01/flash_recovery_area/POLI/backupset/_03_23/o1_mf_ncnnf_TAG0323T234751_8nvmod9y_.bkp tag=TAG0323T234751 comment=NONEchannel ORA_DISK_1: backup set complete, elapsed time: 00:00:01Finished backup at 23-MAR-13Starting Control File Autobackup at 23-MAR-13piece handle=/u01/flash_recovery_area/POLI/autobackup/_03_23/o1_mf_n_810863277_8nvmofjy_.bkp comment=NONEFinished Control File Autobackup at 23-MAR-13
（四）、使用SQL命令备份controlfile
RMAN> sql "alter database backup controlfile to ''/tmp/poli_df.bak''";sql statement: alter database backup controlfile to ''/tmp/poli_df.bak''
