ORA-01548: 已找到活动回退段'_SYSSMU1$'，终止删除表空间 解决办法

验证过程：
1 查看所有回滚段信息：
select segment_name,status,tablespace_name from dba_rollback_segs;
SEGMENT_NAME STATUS TABLESPACE_NAME
------------------------------ ---------------- ------------------------------
SYSTEM ONLINE SYSTEM
_SYSSMU1$ NEEDS RECOVERY UNDOTBS1
_SYSSMU2$ NEEDS RECOVERY UNDOTBS1
_SYSSMU3$ NEEDS RECOVERY UNDOTBS1
_SYSSMU4$ NEEDS RECOVERY UNDOTBS1
_SYSSMU5$ NEEDS RECOVERY UNDOTBS1
_SYSSMU6$ NEEDS RECOVERY UNDOTBS1
_SYSSMU7$ NEEDS RECOVERY UNDOTBS1
_SYSSMU8$ NEEDS RECOVERY UNDOTBS1
_SYSSMU9$ NEEDS RECOVERY UNDOTBS1
_SYSSMU10$ NEEDS RECOVERY UNDOTBS1

SEGMENT_NAME STATUS TABLESPACE_NAME
------------------------------ ---------------- ------------------------------
_SYSSMU11$ OFFLINE UNDOTBS2
_SYSSMU12$ OFFLINE UNDOTBS2
_SYSSMU13$ OFFLINE UNDOTBS2
_SYSSMU14$ OFFLINE UNDOTBS2
_SYSSMU15$ OFFLINE UNDOTBS2
_SYSSMU16$ OFFLINE UNDOTBS2
_SYSSMU17$ OFFLINE UNDOTBS2
_SYSSMU18$ OFFLINE UNDOTBS2
_SYSSMU19$ OFFLINE UNDOTBS2
_SYSSMU20$ OFFLINE UNDOTBS2

已选择21行。
说明是有问题的。

处理过程
1 create undo tablespace undotBS2 datafile 'D:oracleoradataPS30710UNDOTBS2.DBF' size 100m;
alter system set undo_tablespace=undotBS2;
drop tablespace undotbs1 including contents;(进行这部操作的时候会报下面的错)：
ORA-01548: 已找到活动回退段'_SYSSMU1$'，终止删除表空间

2 修改文件init.ora.162007221035，如下：
undo_management=manual
undo_retention=10800
undo_tablespace=undotBS2
_CORRUPTED_ROLLBACK_SEGMENTS =(_SYSSMU1$,_SYSSMU2$,_SYSSMU3$,_SYSSMU3$,_SYSSMU4$,_SYSSMU5$,_SYSSMU6$,_SYSSMU7$,_SYSSMU8$,_SYSSMU9$,_SYSSMU10$)
3 启动服务
startup pfile='D:oracleadminPS30710pfileinit.ora.421200715439'
4 删除表空间
drop tablespace undotbs1 including contents;
create undo tablespace undotBS1 datafile 'D:oracleoradataPS30710UNDOTBS01.DBF' size 200m;
drop tablespace undotBS2 including contents;
5 修改init.ora.162007221035，如下：
undo_management=auto
undo_retention=10800
undo_tablespace=undotBS1
_CORRUPTED_ROLLBACK_SEGMENTS =(_SYSSMU1$,_SYSSMU2$,_SYSSMU3$,_SYSSMU3$,_SYSSMU4$,_SYSSMU5$,_SYSSMU6$,_SYSSMU7$,_SYSSMU8$,_SYSSMU9$,_SYSSMU10$)
6 关闭服务，并且用下面的命令重新启动服务
startup pfile='D:oracleadminPS30710pfileinit.ora.421200715439'
7 拷贝spfile文件，原先的spfile文件做好备份
create spfile='D:oracleora92databaseSPFILEPS30710.ORA' FROM pfile='D:oracleadminPS30710pfileinit.ora.421200715439';
8 关闭服务器，重新启动服务器，即可。
select segment_name,status,tablespace_name from dba_rollback_segs;
SEGMENT_NAME STATUS TABLESPACE_NAME
------------------------------ ---------------- ------------------------------
SYSTEM ONLINE SYSTEM
_SYSSMU1$ ONLINE UNDOTBS1
_SYSSMU2$ ONLINE UNDOTBS1
_SYSSMU3$ ONLINE UNDOTBS1
_SYSSMU4$ ONLINE UNDOTBS1
_SYSSMU5$ ONLINE UNDOTBS1
_SYSSMU6$ ONLINE UNDOTBS1
_SYSSMU7$ ONLINE UNDOTBS1
_SYSSMU8$ ONLINE UNDOTBS1
_SYSSMU9$ ONLINE UNDOTBS1
_SYSSMU10$ ONLINE UNDOTBS1

已选择11行。