undo表空间的数据文件丢失，如果没有备份的情况下，但是redo完好，这个时候可以这样恢复，下边给出一个例子。
undo表空间文件丢失恢复（1）--有备份的情况下恢复：http://blog.itpub.net/26736162/viewspace-1458654/
[oracle@rhel6_lhr ~]$ sqlplus / as sysdba
SQL*Plus: Release 10.2.0.4.0 - Production on Thu Mar 12 18:13:13 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> select name from v$datafile;
NAME
--------------------------------------------------------------------------------
/u03/app/oracle/oradata/ora1024g/system01.dbf
/u03/app/oracle/oradata/ora1024g/undotbs01.dbf
/u03/app/oracle/oradata/ora1024g/sysaux01.dbf
/u03/app/oracle/oradata/ora1024g/users01.dbf
/u03/app/oracle/oradata/ora1024g/example01.dbf
/u03/app/oracle/oradata/ora1024g/undotbs02.dbf
6 rows selected.
SQL> drop table bb;
Table dropped.
SQL> create table bb as select * from user_tables;
Table created.
SQL> insert into bb select * from user_tables;
707 rows created.
SQL> select count(1) from bb;
COUNT(1)
----------
1413
SQL>
SQL>
SQL> ho rm /u03/app/oracle/oradata/ora1024g/undotbs01.dbf
SQL> shutdown abort;
ORACLE instance shut down.
SQL> startup;
ORACLE instance started.
Total System Global Area 448790528 bytes
Fixed Size 2084616 bytes
Variable Size 130023672 bytes
Database Buffers 310378496 bytes
Redo Buffers 6303744 bytes
Database mounted.
ORA-01157: cannot identify/lock data file 2 - see DBWR trace file
ORA-01110: data file 2: '/u03/app/oracle/oradata/ora1024g/undotbs01.dbf'
SQL> show parameter undo
NAME TYPE VALUE
------------------------------------ ----------- ------------------------------
undo_management string AUTO
undo_retention integer 900
undo_tablespace string UNDOTBS1
SQL>
SQL> set line 9999
SQL> col name format a100
SQL> select name,status,enabled from v$datafile;
NAME STATUS ENABLED
---------------------------------------------------------------------------------------------------- ------- ----------
/u03/app/oracle/oradata/ora1024g/system01.dbf SYSTEM READ WRITE
/u03/app/oracle/oradata/ora1024g/undotbs01.dbf ONLINE READ WRITE
/u03/app/oracle/oradata/ora1024g/sysaux01.dbf ONLINE READ WRITE
/u03/app/oracle/oradata/ora1024g/users01.dbf ONLINE READ WRITE
/u03/app/oracle/oradata/ora1024g/example01.dbf ONLINE READ WRITE
/u03/app/oracle/oradata/ora1024g/undotbs02.dbf ONLINE READ WRITE
6 rows selected.
SQL> select * from v$recover_file;
FILE# ONLINE ONLINE_ ERROR CHANGE# TIME
---------- ------- ------- ----------------------------------------------------------------- ---------- ---------
3 OFFLINE OFFLINE FILE NOT FOUND 0
SQL> alter database create datafile 2 as '/u03/app/oracle/oradata/ora1024g/undotbs01.dbf' size 50m;
Database altered.
SQL> select * from v$recover_file;
FILE# ONLINE ONLINE_ ERROR CHANGE# TIME
---------- ------- ------- ----------------------------------------------------------------- ---------- ---------
2 ONLINE ONLINE 1278091 12-MAR-15
SQL> alter database open;
alter database open
*
ERROR at line 1:
ORA-01113: file 2 needs media recovery
ORA-01110: data file 2: '/u03/app/oracle/oradata/ora1024g/undotbs01.dbf'
SQL> select * from v$recover_file;
FILE# ONLINE ONLINE_ ERROR CHANGE# TIME
---------- ------- ------- ----------------------------------------------------------------- ---------- ---------
2 ONLINE ONLINE 1278091 12-MAR-15
SQL> recover datafile 2;
ORA-00279: change 1278091 generated at 03/12/2015 20:14:19 needed for thread 1
ORA-00289: suggestion : /u03/app/oracle/flash_recovery_area/ORA1024G/archivelog/2015_03_13/o1_mf_1_31_%u_.arc
ORA-00280: change 1278091 for thread 1 is in sequence #31
Specify log: {=suggested | filename | AUTO | CANCEL}
auto
ORA-00279: change 1299920 generated at 03/12/2015 20:32:01 needed for thread 1
ORA-00289: suggestion : /u03/app/oracle/flash_recovery_area/ORA1024G/archivelog/2015_03_13/o1_mf_1_32_%u_.arc
ORA-00280: change 1299920 for thread 1 is in sequence #32
ORA-00278: log file '/u03/app/oracle/flash_recovery_area/ORA1024G/archivelog/2015_03_12/o1_mf_1_31_bj31wg6x_.arc' no longer needed for this recovery
ORA-00279: change 1319924 generated at 03/12/2015 20:33:18 needed for thread 1
ORA-00289: suggestion : /u03/app/oracle/flash_recovery_area/ORA1024G/archivelog/2015_03_13/o1_mf_1_33_%u_.arc
ORA-00280: change 1319924 for thread 1 is in sequence #33
ORA-00278: log file '/u03/app/oracle/flash_recovery_area/ORA1024G/archivelog/2015_03_12/o1_mf_1_32_bj31wg77_.arc' no longer needed for this recovery
ORA-00279: change 1339928 generated at 03/12/2015 20:33:59 needed for thread 1
ORA-00289: suggestion : /u03/app/oracle/flash_recovery_area/ORA1024G/archivelog/2015_03_13/o1_mf_1_34_%u_.arc
ORA-00280: change 1339928 for thread 1 is in sequence #34
ORA-00278: log file '/u03/app/oracle/flash_recovery_area/ORA1024G/archivelog/2015_03_12/o1_mf_1_33_bj31xqc4_.arc' no longer needed for this recovery
ORA-00279: change 1359932 generated at 03/12/2015 20:35:20 needed for thread 1
ORA-00289: suggestion : /u03/app/oracle/flash_recovery_area/ORA1024G/archivelog/2015_03_13/o1_mf_1_35_%u_.arc
ORA-00280: change 1359932 for thread 1 is in sequence #35
ORA-00278: log file '/u03/app/oracle/flash_recovery_area/ORA1024G/archivelog/2015_03_12/o1_mf_1_34_bj3208q4_.arc' no longer needed for this recovery
ORA-00279: change 1379936 generated at 03/12/2015 20:36:20 needed for thread 1
ORA-00289: suggestion : /u03/app/oracle/flash_recovery_area/ORA1024G/archivelog/2015_03_13/o1_mf_1_36_%u_.arc
ORA-00280: change 1379936 for thread 1 is in sequence #36
ORA-00278: log file '/u03/app/oracle/flash_recovery_area/ORA1024G/archivelog/2015_03_12/o1_mf_1_35_bj3224vc_.arc' no longer needed for this recovery
ORA-00279: change 1399940 generated at 03/12/2015 20:37:20 needed for thread 1
ORA-00289: suggestion : /u03/app/oracle/flash_recovery_area/ORA1024G/archivelog/2015_03_13/o1_mf_1_37_%u_.arc
ORA-00280: change 1399940 for thread 1 is in sequence #37
ORA-00278: log file '/u03/app/oracle/flash_recovery_area/ORA1024G/archivelog/2015_03_12/o1_mf_1_36_bj32409g_.arc' no longer needed for this recovery
ORA-00279: change 1419945 generated at 03/12/2015 20:40:48 needed for thread 1
ORA-00289: suggestion : /u03/app/oracle/flash_recovery_area/ORA1024G/archivelog/2015_03_13/o1_mf_1_38_%u_.arc
ORA-00280: change 1419945 for thread 1 is in sequence #38
ORA-00278: log file '/u03/app/oracle/flash_recovery_area/ORA1024G/archivelog/2015_03_12/o1_mf_1_37_bj32bj52_.arc' no longer needed for this recovery
ORA-00279: change 1439949 generated at 03/12/2015 20:43:49 needed for thread 1
ORA-00289: suggestion : /u03/app/oracle/flash_recovery_area/ORA1024G/archivelog/2015_03_13/o1_mf_1_39_%u_.arc
ORA-00280: change 1439949 for thread 1 is in sequence #39
ORA-00278: log file '/u03/app/oracle/flash_recovery_area/ORA1024G/archivelog/2015_03_12/o1_mf_1_38_bj32j54p_.arc' no longer needed for this recovery
ORA-00279: change 1459953 generated at 03/12/2015 20:45:50 needed for thread 1
ORA-00289: suggestion : /u03/app/oracle/flash_recovery_area/ORA1024G/archivelog/2015_03_13/o1_mf_1_40_%u_.arc
ORA-00280: change 1459953 for thread 1 is in sequence #40
ORA-00278: log file '/u03/app/oracle/flash_recovery_area/ORA1024G/archivelog/2015_03_12/o1_mf_1_39_bj32mygp_.arc' no longer needed for this recovery
ORA-00279: change 1479957 generated at 03/12/2015 20:48:27 needed for thread 1
ORA-00289: suggestion : /u03/app/oracle/flash_recovery_area/ORA1024G/archivelog/2015_03_13/o1_mf_1_41_%u_.arc
ORA-00280: change 1479957 for thread 1 is in sequence #41
ORA-00278: log file '/u03/app/oracle/flash_recovery_area/ORA1024G/archivelog/2015_03_12/o1_mf_1_40_bj32rv2k_.arc' no longer needed for this recovery
Log applied.
Media recovery complete.
SQL> select name,status,enabled from v$datafile;
NAME STATUS ENABLED
---------------------------------------------------------------------------------------------------- ------- ----------
/u03/app/oracle/oradata/ora1024g/system01.dbf SYSTEM READ WRITE
/u03/app/oracle/oradata/ora1024g/undotbs01.dbf ONLINE READ WRITE
/u03/app/oracle/oradata/ora1024g/sysaux01.dbf ONLINE READ WRITE
/u03/app/oracle/oradata/ora1024g/users01.dbf ONLINE READ WRITE
/u03/app/oracle/oradata/ora1024g/example01.dbf ONLINE READ WRITE
/u03/app/oracle/oradata/ora1024g/undotbs02.dbf ONLINE READ WRITE
6 rows selected.
SQL> select * from v$recover_file;
no rows selected
SQL> alter database open;
Database altered.
SQL> select count(1) from bb;
COUNT(1)
----------
706