Take control of Oracle’s queue with a step by step approach
to getting rid of those pesky DBMS_JOBs.
Let’s face it, Oracle’s job scheduling facility is a
wonderful tool for scheduling Oracle related jobs without having to maintain a
cron job on Unix or an AT job in windows. It is also very robust and reliable.
It is that very reliability and robustness that gives many of us our problems.
If you have any form of jobs running on your system, you
will at one time or another come across the issue of a run-away job that just doesn’t
seem to want to end. Or maybe you will try and shutdown the database only to
find out that it is waiting to complete a job. I would like to offer some help
in the management of those job queues when they just don’t seem to want to end
or go away.
A while back I needed to find information on how to clear
the job queue for jobs running with no apparent end in sight. Some had hung,
while others just were taking a bad access path to data. I needed to bring
down these jobs, do a bit of tuning and then restart the jobs. Well, to my
amazement, there wasn’t very much information out on the web that gave good
insight into this process. Basically the method suggested was to first break
the job and then issue an ALTER SYTEM KILL SESSION command. This method does
not always work and unfortunately–never on my system, for the jobs I had. I
then called Oracle support and basically got the same answer as I found out on
the web. They did give me one added piece of information. They said, if the
ALTER SYSTEM KILL SESSION didn’t work, I was supposed to bounce my database in
order to bring down the job queue processes. First of all, this wasn’t an
option and when I did get the opportunity to bounce the database box, many of
the jobs seemed to come right back as strong as ever.
Before writing this article I did another quick search on
the topic of killing dbms_jobs and to my amazement there still wasn’t much good
information out there. This is why I want to share my method, so that you won’t
be stuck up against the wall with this problem and nowhere to turn, as I was.
Lets first go through a few different methods of viewing the
information about job queues.
Viewing scheduled dbms_jobs
When looking at what jobs have been scheduled, there is
really only one view that you need to go to. The dba_jobs view contains all of
the information you need, to see what has been scheduled, when they were last
run, and if they are currently running. Use the following simple script to take
a look. Bear with me on the sub-select, I will build on this query as we go on
in the presentation.
scheduled_dbms_jobs.sql
set linesize 250
col log_user for a10
col job for 9999999 head ‘Job’
col broken for a1 head ‘B’
col failures for 99 head “fail”
col last_date for a18 head ‘Last|Date’
col this_date for a18 head ‘This|Date’
col next_date for a18 head ‘Next|Date’
col interval for 9999.000 head ‘Run|Interval’
col what for a60select j.log_user,
j.job,
j.broken,
j.failures,
j.last_date||’:’||j.last_sec last_date,
j.this_date||’:’||j.this_sec this_date,
j.next_date||’:’||j.next_sec next_date,
j.next_date – j.last_date interval,
j.what
from (select dj.LOG_USER, dj.JOB, dj.BROKEN, dj.FAILURES,
dj.LAST_DATE, dj.LAST_SEC, dj.THIS_DATE, dj.THIS_SEC,
dj.NEXT_DATE, dj.NEXT_SEC, dj.INTERVAL, dj.WHAT
from dba_jobs dj) j;
What Jobs are Actually Running
A simple join to the dba_jobs_running view will give us a
good handle on the scheduled jobs that are actually running at this time. This
is done by a simple join through the job number. The new column of interest
returned here is the sid which is the identifier of the process that is
currently executing the job.
running_jobs.sql
set linesize 250
col sid for 9999 head ‘Session|ID’
col log_user for a10
col job for 9999999 head ‘Job’
col broken for a1 head ‘B’
col failures for 99 head “fail”
col last_date for a18 head ‘Last|Date’
col this_date for a18 head ‘This|Date’
col next_date for a18 head ‘Next|Date’
col interval for 9999.000 head ‘Run|Interval’
col what for a60
select j.sid,
j.log_user,
j.job,
j.broken,
j.failures,
j.last_date||’:’||j.last_sec last_date,
j.this_date||’:’||j.this_sec this_date,
j.next_date||’:’||j.next_sec next_date,
j.next_date – j.last_date interval,
j.what
from (select djr.SID,
dj.LOG_USER, dj.JOB, dj.BROKEN, dj.FAILURES,
dj.LAST_DATE, dj.LAST_SEC, dj.THIS_DATE, dj.THIS_SEC,
dj.NEXT_DATE, dj.NEXT_SEC, dj.INTERVAL, dj.WHAT
from dba_jobs dj, dba_jobs_running djr
where dj.job = djr.job ) j;
What Sessions are Running the Jobs
Now that we have determined which jobs are currently running, we need to find which Oracle session and operating system process is accessing them.
This is done
through first joining v$process to v$session by way of paddr and addr which is
the address of the processs that owns the sessions, and then joining the
results back to the jobs running through the sid value. The new columns
returned in our query are spid which is the operating system process identifier
and serial# which is the session serial number.
session_jobs.sql
set linesize 250
col sid for 9999 head ‘Session|ID’
col spid head ‘O/S|Process|ID’
col serial# for 9999999 head ‘Session|Serial#’
col log_user for a10
col job for 9999999 head ‘Job’
col broken for a1 head ‘B’
col failures for 99 head “fail”
col last_date for a18 head ‘Last|Date’
col this_date for a18 head ‘This|Date’
col next_date for a18 head ‘Next|Date’
col interval for 9999.000 head ‘Run|Interval’
col what for a60
select j.sid,
s.spid,
s.serial#,
j.log_user,
j.job,
j.broken,
j.failures,
j.last_date||’:’||j.last_sec last_date,
j.this_date||’:’||j.this_sec this_date,
j.next_date||’:’||j.next_sec next_date,
j.next_date – j.last_date interval,
j.what
from (select djr.SID,
dj.LOG_USER, dj.JOB, dj.BROKEN, dj.FAILURES,
dj.LAST_DATE, dj.LAST_SEC, dj.THIS_DATE, dj.THIS_SEC,
dj.NEXT_DATE, dj.NEXT_SEC, dj.INTERVAL, dj.WHAT
from dba_jobs dj, dba_jobs_running djr
where dj.job = djr.job ) j,
(select p.spid, s.sid, s.serial#
from v$process p, v$session s
where p.addr = s.paddr ) s
where j.sid = s.sid;
Now that we have a good handle on how we can look at the
jobs and the key columns involved, let’s go through the steps needed to bring
down a job. The following is a 5 to 11 step process that should solve all of
your problems.
