Killing Oracle Session

We can kill user session using 3

1. The SQL Plus approach

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

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

or

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

2. Using Windows NT Approach

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

C:> orakill ORACLE_SID spid

3. Using Linux/Unix Approach

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

# kill -9 spid
make sure it's worked out with this command
ps -ef | grep ora
       33 364       USER2                          SQLPLUSW.EXE
       33 364       USER2                          SQLPLUSW.EXE

That's all needed steps