Cannot drop undo tablespace with Active extents but no active sessions

Question

Hi all,
I am running on 10gr2 oracle database in a Linux 32 bit environment.
I have a corrupted undo datafile. I've been able to recover the datafile but still the alert logs is still showing that it is corrupted.
Now what I'm trying to do is to drop the old undo tablespace like the one discussed here Change undo tablespace in Oracle - Switch Oracle's Undo tablespace.
My problem is I have an Active extent but no active session corresponding to it:
SYS@ccasdb AS SYSDBA > SELECT a.name,b.status
FROM   v$rollname a,v$rollstat b
WHERE  a.usn = b.usn
AND    a.name IN (
                  SELECT segment_name
                  FROM dba_segments
                  WHERE tablespace_name = 'UNDOTBS1'
                 );  2    3    4    5    6    7    8
NAME                           STATUS
_SYSSMU18$                     PENDING OFFLINE
SYS@ccasdb AS SYSDBA > SELECT a.name,b.status , d.username , d.sid , d.serial#
  2  FROM   v$rollname a,v$rollstat b, v$transaction c , v$session d
  3  WHERE  a.usn = b.usn
  4  AND    a.usn = c.xidusn
  5  AND    c.ses_addr = d.saddr
  6  AND    a.name IN (
  7               SELECT segment_name
  8               FROM dba_segments
  9               WHERE tablespace_name = 'UNDOTBS1'
10              );
no rows selected
but still cannot drop the undotablespace.
SYS@ccasdb AS SYSDBA > drop tablespace UNDOTBS1 including contents and datafiles;
drop tablespace UNDOTBS1 including contents and datafiles
ERROR at line 1:
ORA-30013: undo tablespace 'UNDOTBS1' is currently in use
Regards,
Tim

Answer 1

Yes i was able to recover the datafile but the alert_log kept on prompting that it is still corrupted. The datafile's status is online.
I want to kill the session/s contributing to the PENDING OFFLINE status of the rollback segment so I can already drop the undotablespace and so
that the alert log will stop prompting for that corrupted datafile in that UNDOTABLESPACE.
Can i Just alter the tablespace's datafiles to offline drop then just drop it. Then I drop the tablespace?