ORA-00026

This was tested on Oracle 9. When you use the ALTER SYSTEM KILL SESSION command, you must supply the SID and SERIAL# from an entry in V$SESSION. You get an ORA-00026 if you do not provide one: 

SQL> alter system kill session

  2  /

alter system kill session

                        *

ERROR at line 1:

ORA-00026: missing or invalid session ID

 

SQL>

 

The SID and SERIAL# are both numbers so you also get an ORA-00026 if you give non numeric values:

 

SQL> alter system kill session 'A,B'

  2  /

alter system kill session 'A,B'

*

ERROR at line 1:

ORA-00026: missing or invalid session ID

 

SQL>

 

… or values which do not come from V$SESSION:

 

SQL> select count(*) from v$session

  2  where sid = 123

  3  and serial# = 456

  4  /

 

  COUNT(*)

----------

         0

 

SQL> alter system kill session '123,456'

  2  /

alter system kill session '123,456'

*

ERROR at line 1:

ORA-00026: missing or invalid session ID

 

SQL>

 

However, if the values are valid, the command should work:

 

SQL> select sid, serial# from v$session

  2  where username = 'ANDREW'

  3  /

 

       SID    SERIAL#

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

        13         34

 

SQL> alter system kill session '13,34'

  2  /

 

System altered.

 

SQL>