SYS@orcl11g>select name,status$ from undo$;
NAME STATUS$
------------------------------------------------------------ ----------
SYSTEM 3
_SYSSMU1_3780397527$ 2
_SYSSMU2_2232571081$ 2
_SYSSMU3_2097677531$ 2
_SYSSMU4_1152005954$ 2
_SYSSMU5_1527469038$ 2
_SYSSMU6_2443381498$ 2
_SYSSMU7_3286610060$ 2
_SYSSMU8_2012382730$ 2
_SYSSMU9_1424341975$ 2
_SYSSMU10_3550978943$ 3
_SYSSMU11_3909920883$ 3
_SYSSMU12_3182721254$ 3
_SYSSMU13_3717211136$ 3
_SYSSMU14_3021863913$ 3
_SYSSMU15_444141832$ 3
_SYSSMU16_3035903491$ 3
_SYSSMU17_178842559$ 3
_SYSSMU18_2539622763$ 3
_SYSSMU19_3920348761$ 3
_SYSSMU20_3705739785$ 3
强制将该回滚段offline，发现还是无法删除：
SYS@orcl11g>alter rollback segment "_SYSSMU10_3550978943$" offline;
Rollback segment altered.
SYS@orcl11g>drop tablespace UNDOTBS1;
drop tablespace UNDOTBS1
*
ERROR at line 1:
ORA-30013: undo tablespace 'UNDOTBS1' is currently in use
此时，我们关闭数据库使用bbed更改该回滚段的状态：
在数据库启动的时候，我们可以是oradebug 10046事件追踪，通过trace文件分析: