1、启动数据库，发现错误
startup
2、查看是否是undo文件损坏引起，并查看是否是当前undo，不是当前undo直接offline，然后open数据库，再删除掉该数据该undo即可
select a.ts#,a.name,b.name from v$datafile a,v$tablespace b where a.ts#=b.ts#;
show parameter undo_tablespace;
3、损坏undo离线，创建pfile文件
alter database datafile n offline drop;
create pfile=’/tmp/pfile’ from spfile;
4、打开数据库,如果打开失败，请继续5，如果成功按照undo异常处理步骤（10g）方法处理
alter database open;
5、如果数据库不能正常打开，而是提示，如下错误：
ERROR at line 1:
ORA-01092: ORACLE instance terminated. Disconnection forced
6、检查日志文件，发现如下：
SMON: about to recover undo segment 21
SMON: mark undo segment 21 as needs recovery
SMON: about to recover undo segment 22
SMON: mark undo segment 22 as needs recovery
SMON: about to recover undo segment 23
SMON: mark undo segment 23 as needs recovery
SMON: about to recover undo segment 24
SMON: mark undo segment 24 as needs recovery
SMON: about to recover undo segment 25
SMON: mark undo segment 25 as needs recovery
SMON: about to recover undo segment 26
SMON: mark undo segment 26 as needs recovery
SMON: about to recover undo segment 27
SMON: mark undo segment 27 as needs recovery
SMON: about to recover undo segment 28
SMON: mark undo segment 28 as needs recovery
SMON: about to recover undo segment 29
SMON: mark undo segment 29 as needs recovery
SMON: about to recover undo segment 30
SMON: mark undo segment 30 as needs recovery
7、编辑pfile文件，内容为
*.undo_management=’MANUAL’
*._allow_resetlogs_corruption=true
*._corrupted_rollback_segments=(_SYSSMU21$,_SYSSMU22$,_SYSSMU23$,_SYSSMU24$,
_SYSSMU25$,_SYSSMU26$,_SYSSMU27$,_SYSSMU28$,_SYSSMU29$,_SYSSMU30$)
*.undo_tablespace=’SYSTEM’
8、退出当前sqlplus，重新登录，利用pfile启动数据库
startup
9、创建新undo表空间
CREATE UNDO TABLESPACE UNDOTBSNEW DATAFILE
‘/opt/oracle/oradata/xifenfei/UNDOTBS01.dbf
SIZE 50M autoextend on next 10m maxsize 30G;
10、查询回滚段信息，为下面删除损坏undo的回滚段做到心中有底
select segment_name,status from dba_rollback_segs;
11、删除损坏undo
drop tablespace UNDOTBSOLD including contents and datafiles;
12、查看回滚段状态
select segment_name,status from dba_rollback_segs;
13、如果有损坏表空间回滚段还存在，手工删除
drop rollback segment “_SYSSMUx$”;
14、修改pfile内容
*.undo_management=’AUTO’
#*._allow_resetlogs_corruption=true
#*._corrupted_rollback_segments=(_SYSSMU21$,_SYSSMU22$,_SYSSMU23$,_SYSSMU24$,
_SYSSMU25$,_SYSSMU26$,_SYSSMU27$,_SYSSMU28$,_SYSSMU29$,_SYSSMU30$)
*.undo_tablespace=’UNDOTBSNEW’
15、重启数据库
shutdown immediate
startup
说明：可以先删除需要恢复的回滚段，再删除损坏的undo表空间