undo表空间的数据文件丢失，如果有备份的情况下，恢复非常简单，下边给出一个例子：
[oracle@rhel6_lhr ~]$ sqlplus / as sysdba
SQL*Plus: Release 10.2.0.4.0 - Production on Thu Mar 12 18:02:13 2015
Copyright (c) 1982, 2007, Oracle. All Rights Reserved.
Connected to:
Oracle Database 10g Enterprise Edition Release 10.2.0.4.0 - 64bit Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options
SQL> archive log list;
Database log mode Archive Mode
Automatic archival Enabled
Archive destination USE_DB_RECOVERY_FILE_DEST
Oldest online log sequence 1
Next log sequence to archive 2
Current log sequence 2
SQL> exit
Disconnected from Oracle Database 10g Enterprise Edition Release 10.2.0.4.0 - 64bit Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options
[oracle@rhel6_lhr ~]$ rman target /
Recovery Manager: Release 10.2.0.4.0 - Production on Thu Mar 12 18:02:23 2015
Copyright (c) 1982, 2007, Oracle. All rights reserved.
connected to target database: ORA1024G (DBID=2698093861)
RMAN> backup database;
Starting backup at 2015-03-12 18:02:30
using target database control file instead of recovery catalog
allocated channel: ORA_DISK_1
channel ORA_DISK_1: sid=144 devtype=DISK
channel ORA_DISK_1: starting full datafile backupset
channel ORA_DISK_1: specifying datafile(s) in backupset
input datafile fno=00001 name=/u03/app/oracle/oradata/ora1024g/system01.dbf
input datafile fno=00003 name=/u03/app/oracle/oradata/ora1024g/sysaux01.dbf
input datafile fno=00005 name=/u03/app/oracle/oradata/ora1024g/example01.dbf
input datafile fno=00002 name=/u03/app/oracle/oradata/ora1024g/undotbs01.dbf
input datafile fno=00004 name=/u03/app/oracle/oradata/ora1024g/users01.dbf
channel ORA_DISK_1: starting piece 1 at 2015-03-12 18:02:31
channel ORA_DISK_1: finished piece 1 at 2015-03-12 18:03:49
piece handle=/u03/app/oracle/flash_recovery_area/ORA1024G/backupset/2015_03_12/o1_mf_nnndf_TAG20150312T180231_bj2s1vh3_.bkp tag=TAG20150312T180231 comment=NONE
channel ORA_DISK_1: backup set complete, elapsed time: 00:01:19
channel ORA_DISK_1: starting full datafile backupset
channel ORA_DISK_1: specifying datafile(s) in backupset
including current control file in backupset
including current SPFILE in backupset
channel ORA_DISK_1: starting piece 1 at 2015-03-12 18:03:53
channel ORA_DISK_1: finished piece 1 at 2015-03-12 18:03:54
piece handle=/u03/app/oracle/flash_recovery_area/ORA1024G/backupset/2015_03_12/o1_mf_ncsnf_TAG20150312T180231_bj2s49dm_.bkp tag=TAG20150312T180231 comment=NONE
channel ORA_DISK_1: backup set complete, elapsed time: 00:00:03
Finished backup at 2015-03-12 18:03:54
RMAN> report schema;
Report of database schema
List of Permanent Datafiles
===========================
File Size(MB) Tablespace RB segs Datafile Name
---- -------- -------------------- ------- ------------------------
1 480 SYSTEM *** /u03/app/oracle/oradata/ora1024g/system01.dbf
2 30 UNDOTBS1 *** /u03/app/oracle/oradata/ora1024g/undotbs01.dbf
3 250 SYSAUX *** /u03/app/oracle/oradata/ora1024g/sysaux01.dbf
4 5 USERS *** /u03/app/oracle/oradata/ora1024g/users01.dbf
5 100 EXAMPLE *** /u03/app/oracle/oradata/ora1024g/example01.dbf
List of Temporary Files
=======================
File Size(MB) Tablespace Maxsize(MB) Tempfile Name
---- -------- -------------------- ----------- --------------------
1 20 TEMP 32767 /u03/app/oracle/oradata/ora1024g/temp01.dbf
RMAN> exit
Recovery Manager complete.
[oracle@rhel6_lhr ~]$ rm /u03/app/oracle/oradata/ora1024g/undotbs01.dbf
[oracle@rhel6_lhr ~]$ sqlplus / as sysdba
SQL*Plus: Release 10.2.0.4.0 - Production on Thu Mar 12 18:05:00 2015
Copyright (c) 1982, 2007, Oracle. All Rights Reserved.
Connected to:
Oracle Database 10g Enterprise Edition Release 10.2.0.4.0 - 64bit Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options
SQL> startup force;
ORACLE instance started.
Total System Global Area 448790528 bytes
Fixed Size 2084616 bytes
Variable Size 130023672 bytes
Database Buffers 310378496 bytes
Redo Buffers 6303744 bytes
Database mounted.
ORA-01157: cannot identify/lock data file 2 - see DBWR trace file
ORA-01110: data file 2: '/u03/app/oracle/oradata/ora1024g/undotbs01.dbf'
SQL> exit
Disconnected from Oracle Database 10g Enterprise Edition Release 10.2.0.4.0 - 64bit Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options
[oracle@rhel6_lhr ~]$ rman target /
Recovery Manager: Release 10.2.0.4.0 - Production on Thu Mar 12 18:05:37 2015
Copyright (c) 1982, 2007, Oracle. All rights reserved.
connected to target database: ORA1024G (DBID=2698093861, not open)
RMAN> restore tablespace undotbs1;
Starting restore at 2015-03-12 18:05:56
using target database control file instead of recovery catalog
allocated channel: ORA_DISK_1
channel ORA_DISK_1: sid=156 devtype=DISK
channel ORA_DISK_1: starting datafile backupset restore
channel ORA_DISK_1: specifying datafile(s) to restore from backup set
restoring datafile 00002 to /u03/app/oracle/oradata/ora1024g/undotbs01.dbf
channel ORA_DISK_1: reading from backup piece /u03/app/oracle/flash_recovery_area/ORA1024G/backupset/2015_03_12/o1_mf_nnndf_TAG20150312T180231_bj2s1vh3_.bkp
channel ORA_DISK_1: restored backup piece 1
piece handle=/u03/app/oracle/flash_recovery_area/ORA1024G/backupset/2015_03_12/o1_mf_nnndf_TAG20150312T180231_bj2s1vh3_.bkp tag=TAG20150312T180231
channel ORA_DISK_1: restore complete, elapsed time: 00:00:06
Finished restore at 2015-03-12 18:06:03
RMAN> recover tablespace undotbs1;
Starting recover at 2015-03-12 18:06:17
using channel ORA_DISK_1
starting media recovery
media recovery complete, elapsed time: 00:00:02
Finished recover at 2015-03-12 18:06:19
RMAN> alter database open;
database opened
--注意这里一定要让undo在线
RMAN> sql 'alter database datafile 2 online';
using target database control file instead of recovery catalog
sql statement: alter database datafile 2 online
RMAN> exit
RMAN> report schema;
Report of database schema
List of Permanent Datafiles
===========================
File Size(MB) Tablespace RB segs Datafile Name
---- -------- -------------------- ------- ------------------------
1 480 SYSTEM *** /u03/app/oracle/oradata/ora1024g/system01.dbf
2 30 UNDOTBS1 *** /u03/app/oracle/oradata/ora1024g/undotbs01.dbf
3 250 SYSAUX *** /u03/app/oracle/oradata/ora1024g/sysaux01.dbf
4 5 USERS *** /u03/app/oracle/oradata/ora1024g/users01.dbf
5 100 EXAMPLE *** /u03/app/oracle/oradata/ora1024g/example01.dbf
List of Temporary Files
=======================
File Size(MB) Tablespace Maxsize(MB) Tempfile Name
---- -------- -------------------- ----------- --------------------
1 20 TEMP 32767 /u03/app/oracle/oradata/ora1024g/temp01.dbf
RMAN>
RMAN>