Oracle UNDO表空间损坏时的处理办法
前两天一客户的Oracle数据库出现故障，通过分析日志发现是UNDOTBS1表空间损坏，在没有使用RMAN备份来做恢复的情况下，通过重建UNDO表空间解决；
拿到这个问题后，先尝试直接 recover database数据库，如果是在正常关闭数据库的情况下undo损坏，则这种方法应该可以修复数据库，如果不是，则可能不行。
尝试重建undo表空间：
首先可知是文件2发生错误，进而导致600错误。
因此，先查看文件2的名字，如下：
SQL> connect sys/manager as sysdba
Connected to an idle instance.
SQL> startup mount pfile='d:/oracle92/ora92/database/inittest.ora'
ORACLE instance started.
Total System Global Area 93395628 bytes
Fixed Size 453292 bytes
Variable Size 75497472 bytes
Database Buffers 16777216 bytes
Redo Buffers 667648 bytes
Database mounted.
SQL> select file#,status,name from v$datafile;
FILE# STATUS
---------- -------
NAME
--------------------------------------------------------------------------------
1 SYSTEM
D:/ORACLE92/ORADATA/TEST/SYSTEM01.DBF
2 ONLINE
D:/ORACLE92/ORADATA/TEST/UNDOTBS01.DBF
3 ONLINE
D:/ORACLE92/ORADATA/TEST/CWMLITE01.DBF
FILE# STATUS
---------- -------
NAME
--------------------------------------------------------------------------------
4 ONLINE
D:/ORACLE92/ORADATA/TEST/DRSYS01.DBF
5 ONLINE
D:/ORACLE92/ORADATA/TEST/EXAMPLE01.DBF
6 ONLINE
D:/ORACLE92/ORADATA/TEST/INDX01.DBF
FILE# STATUS
---------- -------
NAME
--------------------------------------------------------------------------------
7 ONLINE
D:/ORACLE92/ORADATA/TEST/ODM01.DBF
8 ONLINE
D:/ORACLE92/ORADATA/TEST/TOOLS01.DBF
9 ONLINE
D:/ORACLE92/ORADATA/TEST/USERS01.DBF
FILE# STATUS
---------- -------
NAME
--------------------------------------------------------------------------------
10 ONLINE
D:/ORACLE92/ORADATA/TEST/XDB01.DBF
11 ONLINE
D:/ORACLE92/ORADATA/TEST/PMS.ORA
12 ONLINE
D:/ORACLE92/ORADATA/TEST/FYBX.ORA
12 rows selected.
可以看到，损坏的文件2是undotbs01.dbf,
查看资料，undotbs损坏或丢失时可以采用隐含参数临时启动数据库，然后进行修复。
修改init文件,加入
*._allow_resetlogs_corruption=true
（注：允许在数据库文件SCN不一致的情况下启动数据库）
*._corrupted_rollback_segments=(_SYSSMU1$,_SYSSMU2$,_SYSSMU3$,_SYSSMU4$,_SYSSMU5$,_SYSSMU6$,_SYSSMU7$,_SYSSMU8$,_SYSSMU9$,_SYSSMU10$)
（注：允许在rollback segments损坏的情况下启动数据库）
SQL> shutdown abort
ORACLE instance shut down.
SQL> startup pfile='d:/oracle92/ora92/database/inittest.ora'
ORACLE instance started.
Total System Global Area 93395628 bytes
Fixed Size 453292 bytes
Variable Size 75497472 bytes
Database Buffers 16777216 bytes
Redo Buffers 667648 bytes
Database mounted.
Database opened.
启动成功，查看下当前的rollback segments
SQL> select segment_name,status from dba_rollback_segs;
SEGMENT_NAME STATUS
------------------------------ ----------------
SYSTEM ONLINE
_SYSSMU1$ NEEDS RECOVERY
_SYSSMU2$ NEEDS RECOVERY
_SYSSMU3$ NEEDS RECOVERY
_SYSSMU4$ NEEDS RECOVERY
_SYSSMU5$ NEEDS RECOVERY
_SYSSMU6$ NEEDS RECOVERY
_SYSSMU7$ NEEDS RECOVERY
_SYSSMU8$ NEEDS RECOVERY
_SYSSMU9$ NEEDS RECOVERY
_SYSSMU10$ NEEDS RECOVERY
SEGMENT_NAME STATUS
------------------------------ ----------------
_SYSSMU11$ ONLINE
12 rows selected.
新建一重做表空间undo
SQL> create undo tablespace undo datafile 'D:/oracle92/oradata/test/undo01.dbf' size 50M reuse autoextend on;
Tablespace created.
SQL> select segment_name,status from dba_rollback_segs;
SEGMENT_NAME STATUS
------------------------------ ----------------
SYSTEM ONLINE
_SYSSMU1$ OFFLINE
_SYSSMU2$ NEEDS RECOVERY
_SYSSMU3$ NEEDS RECOVERY
_SYSSMU4$ NEEDS RECOVERY
_SYSSMU5$ NEEDS RECOVERY
_SYSSMU6$ NEEDS RECOVERY
_SYSSMU7$ NEEDS RECOVERY
_SYSSMU8$ NEEDS RECOVERY
_SYSSMU9$ NEEDS RECOVERY
_SYSSMU10$ NEEDS RECOVERY
SEGMENT_NAME STATUS
------------------------------ ----------------
_SYSSMU11$ ONLINE
_SYSSMU12$ OFFLINE
_SYSSMU13$ OFFLINE
_SYSSMU14$ OFFLINE
_SYSSMU15$ OFFLINE
_SYSSMU16$ OFFLINE
_SYSSMU17$ OFFLINE
_SYSSMU18$ OFFLINE
_SYSSMU19$ OFFLINE
_SYSSMU20$ OFFLINE
_SYSSMU21$ OFFLINE
22 rows selected.
SQL> shutdown immediate
Database closed.
Database dismounted.
ORACLE instance shut down.
修改init文件，指定默认表空间为新建的表空间
*.undo_tablespace=undo
SQL> startup pfile='d:/oracle92/ora92/database/inittest.ora'
ORACLE instance started.
Total System Global Area 93395628 bytes
Fixed Size 453292 bytes
Variable Size 75497472 bytes
Database Buffers 16777216 bytes
Redo Buffers 667648 bytes
Database mounted.
Database opened.
删除损坏的undotbs1表空间：
SQL> alter tablespace undotbs1 offline normal;
这个地方，如果查询undotbs1对应的数据文件的状态是recover状态时，是无法offline的，此时我是直接通过下面的命令删除了。
Tablespace altered.
SQL> drop tablespace UNDOTBS1 including contents and datafiles;
Tablespace dropped.
SQL> select * from v$recover_file;
no rows selected
SQL> shutdown immediate
Database closed.
Database dismounted.
ORACLE instance shut down.
修改init文件,注释参数
#*._allow_resetlogs_corruption=true
#*._corrupted_rollback_segments=(_SYSSMU1$,_SYSSMU2$,_SYSSMU3$,_SYSSMU4$,_SYSSMU5$,_SYSSMU6$,_SYSSMU7$,_SYSSMU8$,_SYSSMU9$,_SYSSMU10$)
SQL> startup pfile='d:/oracle92/ora92/database/inittest.ora'
ORACLE instance started.
Total System Global Area 93395628 bytes
Fixed Size 453292 bytes
Variable Size 75497472 bytes
Database Buffers 16777216 bytes
Redo Buffers 667648 bytes
Database mounted.
Database opened.
SQL>
至此数据库已经成功修复。
**********************************************************************************
需要提醒的是，在删除损坏的重做表空间时，一定要先offline，
否则注释掉隐含参数后就会出现下面的情况。
SQL> startup pfile='d:/oracle92/ora92/database/inittest.ora'
ORACLE instance started.
Total System Global Area 93395628 bytes
Fixed Size 453292 bytes
Variable Size 75497472 bytes
Database Buffers 16777216 bytes
Redo Buffers 667648 bytes
Database mounted.
ORA-01092: ORACLE instance terminated. Disconnection forced
查看alert log，本例中会发现下面的信息，oracle标记刚才删除的
重做表空间需要恢复，这时就无法去掉隐含参数了。
......
drop tablespace UNDOTBS1 including contents and datafiles
SMON: about to recover undo segment 6
SMON: mark undo segment 6 as needs recovery
SMON: about to recover undo segment 6
SMON: mark undo segment 6 as needs recovery
SMON: about to recover undo segment 6
SMON: mark undo segment 6 as needs recovery