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Sessions can be killed from within oracle using the ALTER SYSTEM KILL SESSION syntax.

First identify the offending session as follows:

SELECT s.sid,
       s.serial#,
       s.osuser,
       s.program
FROM   v$session s;

       SID    SERIAL# OSUSER                         PROGRAM
---------- ---------- ------------------------------ ---------------
         1          1 SYSTEM                         ORACLE.EXE
         2          1 SYSTEM                         ORACLE.EXE
         3          1 SYSTEM                         ORACLE.EXE
         4          1 SYSTEM                         ORACLE.EXE
         5          1 SYSTEM                         ORACLE.EXE
         6          1 SYSTEM                         ORACLE.EXE
        20         60 SYSTEM                         DBSNMP.EXE
        43      11215 USER1                          SQLPLUSW.EXE
        33       5337 USER2                          SQLPLUSW.EXE

The SID and SERIAL# values of the relevant session can then be substituted into the following statement:

SQL> ALTER SYSTEM KILL SESSION 'sid,serial#';

In some situations the Oracle.exe is not able to kill the session immediately. In these cases the session will be “marked for kill”. It will then be killed as soon as possible.

Issuing the ALTER SYSTEM KILL SESSION command is the only safe way to kill an Oracle session. If the marked session persists for some time you may consider killing the process at the operating system level, as explained below. Killing OS processes is dangerous and can lead to instance failures, so do this at your own peril.

It is possible to force the kill by adding the IMMEDIATE keyword:

SQL> ALTER SYSTEM KILL SESSION 'sid,serial#' IMMEDIATE;

This should prevent you ever needing to use the orakill.exe in Windows, or the kill command in UNIX/Linux.

The NT Approach

To kill the session via the NT operating system, first identify the session as follows:

SELECT s.sid,
       p.spid,
       s.osuser,
       s.program
FROM   v$process p,
       v$session s
WHERE  p.addr = s.paddr;

       SID SPID      OSUSER                         PROGRAM
---------- --------- ------------------------------ ---------------
         1 310       SYSTEM                         ORACLE.EXE
         2 300       SYSTEM                         ORACLE.EXE
         3 309       SYSTEM                         ORACLE.EXE
         4 299       SYSTEM                         ORACLE.EXE
         5 302       SYSTEM                         ORACLE.EXE
         6 350       SYSTEM                         ORACLE.EXE
        20 412       SYSTEM                         DBSNMP.EXE
        43 410       USER1                          SQLPLUSW.EXE
        33 364       USER2                          SQLPLUSW.EXE

The SID and SPID values of the relevant session can then be substituted into the following command issued from the command line:

C:> orakill ORACLE_SID spid

The session thread should be killed immediately and all resources released.

The UNIX Approach

To kill the session via the UNIX operating system, first identify the session in the same way as the NT approach, then substitute the relevant SPID into the following command:

% kill spid

If after a few minutes the process hasn’t stopped, terminate the session using:

% kill -9 spid

If in doubt check that the SPID matches the UNIX PROCESSID shown using:

% ps -ef | grep ora

The session thread should be killed immediately and all resources released.