How to remove an internal job in Oracle?

In order to stop job you need to find job name and description (what).
You can find all columns from dba_jobs view below:

SQL> desc dba_jobs
 Name                                      Null?    Type
 ----------------------------------------- -------- ---------------------
 JOB                                       NOT NULL NUMBER
 LOG_USER                                  NOT NULL VARCHAR2(30)
 PRIV_USER                                 NOT NULL VARCHAR2(30)
 SCHEMA_USER                               NOT NULL VARCHAR2(30)
 LAST_DATE                                          DATE
 LAST_SEC                                           VARCHAR2(8)
 THIS_DATE                                          DATE
 THIS_SEC                                           VARCHAR2(8)
 NEXT_DATE                                 NOT NULL DATE
 NEXT_SEC                                           VARCHAR2(8)
 TOTAL_TIME                                         NUMBER
 BROKEN                                             VARCHAR2(1)
 INTERVAL                                  NOT NULL VARCHAR2(200)
 FAILURES                                           NUMBER
 WHAT                                               VARCHAR2(4000)
 NLS_ENV                                            VARCHAR2(4000)
 MISC_ENV                                           RAW(32)
 INSTANCE                                           NUMBER

SQL>
SQL> select job from dba_jobs;
JOB
----------
40
22
65
41
If you need to stop all jobs temporary you can do the following:

SQL> Show parameter job_queue_processes

NAME                                 TYPE        VALUE
------------------------------------ ----------- -------------------------
job_queue_processes                  integer     10

SQL>alter system set job_queue_processes = 0 scope=both;

Reset the parameter to what it was later.


If a job fails to execute after 16 attempts Oracle will mark it as broken and stop running it.
This will be indicated by a ‘Y’ in the BROKEN column of the dba_jobs view.
If you want to tell Oracle to not run an specific job you can manually mark it as broken by executing the following:

BEGIN
DBMS_JOB.BROKEN(JOB => 22, BROKEN => TRUE);
END;
/

It will be remained broken and will not be run until you either force it to run or mark it to not broken.
When marking it as not broken you must also specify the next date for the job to run.
The following will mark job 22 as not broken and have it execute at 10:00pm on Feb 20.

BEGIN
DBMS_JOB.BROKEN(JOB => 22, BROKEN => FALSE, NEXT_DATE => TO_DATE('22:00 02/20/12', 'HH24:MI MM/DD/YY'));
END;
/
Or 
you jut can start the job based on it's schedule:
EXECUTE DBMS_JOB.BROKEN(JOB => 22, BROKEN => FALSE);

commit;

Or

You asked to kill whole session:

First, find the session number and sid id from v$session then:

alter system kill session 'sid, serial#' 


To remove a job from Oracle job queue you  need the job number.
If you’re not sure what to do, you should be able to find it by querying from dba_jobs view.

When you have the job number, run the following command:

BEGIN
DBMS_JOB.REMOVE(JOB => 22);
END;
/

Or
To completely remove a job:

SQL> execute dbms_job.remove(22); 

If you asked to kill a session in windows you can find the  tread first and then kill by orakill command:

First find the sid and thread you want to kill by using the following  query:

SELECT sid, spid as thread, osuser, s.program

FROM sys.v_$process p, sys.v_$session s 

WHERE p.addr = s.paddr

Then run the following for Oracle on Windows :

C:\>orakill sid thread

For example:
C:\>orakill ORCL 4760
Kill of thread id 4760 in instance ORCL successfully signalled.

Attention: the sid here is the name  given to database.

As we see above, you might ask why Oracle provide orakill utility when you can kill a session by alter system kill.

1) The alter system will not clear any lock and the session will be remained until

it times out. But orakill kill the session instantly.

2)If a DBA can't have access to Sql Plus because all resource is in used then the session can be killed without longing to database. 

Unlike the Unix, windows is thread-based which means for each instance all background processes and sessions has oracle.exe process, then you need to find the thread number to kill specific session. On the other hand orakill serves the action "kill -9 " does in Unix.

Related link:

http://www.oracleutilities.com/OSUtil/orakill.html