How to Kill Oracle Sessions
Make sure you know what you are doing There are a number of ways to kill rogue sessions both within Oracle and externally. The first step is to identify the session to be killed by gv$sessions.
The basic syntax for killing a session is shown below.
SQL> ALTER SYSTEM KILL SESSION 'sid,serial#';
In a RAC environment, you optionally specify the INST_ID, shown when querying the GV$SESSION view. This allows you to kill a session on different RAC node.
SQL> ALTER SYSTEM KILL SESSION 'sid,serial#@inst_id';
The KILL SESSION command doesn't actually kill the session. It merely asks the session to kill itself. In some situations, like waiting for a reply from a remote database or rolling back transactions, the session will not kill itself immediately and will wait for the current operation to complete. In these cases the session will have a status of "marked for kill". It will then be killed as soon as possible.
In addition to the syntax described above, you can add the IMMEDIATE clause.
SQL> ALTER SYSTEM KILL SESSION 'sid,serial#' IMMEDIATE;
This does not affect the work performed by the command, but it returns control back to the current session immediately, rather than waiting for confirmation of the kill.
If the marked session persists for some time you may consider killing the process at the operating system level. Before doing this it's worth checking to see if it is performing a rollback. If the USED_UREC value is decreasing for the session in question you should leave it to complete the rollback rather than killing the session at the operating system level.
Oracle 11g introduced the ALTER SYSTEM DISCONNECT SESSION syntax as a new method for killing Oracle sessions. Unlike the KILL SESSION command which asks the session to kill itself, the DISCONNECT SESSION command kills the dedicated server process (or virtual circuit when using Shared Sever), which is equivalent to killing the server process from the operating system. The basic syntax is similar to the KILL SESSION command with the addition of the POST_TRANSACTION clause. The SID and SERIAL# values of the relevant session can be substituted into one of the following statements.
SQL> ALTER SYSTEM DISCONNECT SESSION 'sid,serial#' POST_TRANSACTION;
SQL> ALTER SYSTEM DISCONNECT SESSION 'sid,serial#' IMMEDIATE;
The POST_TRANSACTION clause waits for ongoing transactions to complete before disconnecting the session, while the IMMEDIATE clause disconnects the session and ongoing transactions are recovered immediately.
To kill the session on the Windows operating system, first identify the session, then substitute the relevant SID and SPID values 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.
To kill the session on UNIX or Linux operating systems, first identify the session, 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 the following.
% 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.
