CANNOT KILL SESSION

@1

Hello,

Do you please know why oracle cannot find the session to kill please?,

p1gnf1d1 > select inst_id,sid,serial#,state from gv$session where sid=168 and serial#=45640;

   INST_ID        SID    SERIAL# STATE

---------- ---------- ---------- -------------------

         1        168      45640 WAITING

p1gnf1d1 > ALTER SYSTEM KILL SESSION '168,45640,@1';

ALTER SYSTEM KILL SESSION '168,45640,@1'

*

ERROR at line 1:

ORA-00030: User session ID does not exist.

Thank You