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dbms_job Tips

Oracle Tips by Burleson Consulting
Don Burleson

For more Oracle dbms_job working details and a complete code depot, see the wonderful $16.95 book Oracle Job Scheduling by Dr. Timothy Hall.  You can get the best deal (30%-off by) buying it directly from the publisher.

The Oracle docs note that the dbms_job package was superceded by the dbms_scheduler package. When administering jobs to manage system load, they suggest disabling dbms_job.  This is accomplished by revoking the package execution priv for users.

For Oracle10g see Oracle dbms_scheduler examples.


 

 


As a review, the dbms_job.submit procedure accepts three parameters, the name of the job to submit, the start time for the job, and the interval to execute the job:

dbms_job.submit(
   what=>'statspack_alert.sql;',

   next_date=>sysdate+1/24, -- start next hour
   interval=>'sysdate+1/24');  -- Run every hour

The problem with this dbms_job procedure is that while we specify the initial start time and re-execution interval, we do not see a mechanism for running the job during predetermined hours during the day.  For example, how do we use dbms_job to start a job at 8:00 AM, run it hourly, and then stop at 5:00 PM?

The example about will use dbms_job to schedule the job to run hourly, but to get time intervals, it is necessary to create two other jobs, one to break the job at 5:00 PM and another to un-break the job the following morning at 8:00 AM.

For advanced scheduling purposes we can create customized job intervals using dbms_job such that start and stop at specified intervals.  Here are some working Oracle dbms_job scheduling frequency examples:

The following examples show how to use these procedures to schedule the my_job_proc procedure to run immediately, then once every hour after that:

BEGIN
DBMS_JOB.isubmit (
job => 99,
what => 'my_job_proc(''DBMS_JOB.ISUBMIT Example.'');',
next_date => SYSDATE,
interval => 'SYSDATE + 1/24 /* 1 Hour */');

COMMIT;
END;
/

 

--
--  Schedule a snapshot to be run on this instance every hour
 
variable jobno number;
variable instno number;
begin
 
  select instance_number into :instno from v$instance;
-- ------------------------------------------------------------
-- Submit job to begin at 0600 and run every hour
-- ------------------------------------------------------------
dbms_job.submit(
   :jobno, 'BEGIN statspack_alert_proc; END;',
   trunc(sysdate)+6/24,
   'trunc(SYSDATE+1/24,''HH'')',
   TRUE,
   :instno);
 
-- ------------------------------------------------------------
-- Submit job to begin at 0900 and run 12 hours later
-- ------------------------------------------------------------
dbms_job.submit(
   :jobno,
   'BEGIN statspack_alert_proc; END;',
   trunc(sysdate+1)+9/24,
   'trunc(SYSDATE+12/24,''HH'')',
   TRUE,
   :instno);
 
-- ------------------------------------------------------------
-- Submit job to begin at 0600 and run every 10 minutes
-- ------------------------------------------------------------
dbms_job.submit(
:jobno,
'BEGIN statspack_alert_proc; END;',
trunc(sysdate+1)+6/24,
'trunc(sysdate+1/144,''MI'')',
TRUE,
:instno);
 
-- ----------------------------------------------------------
-- Submit job to begin at 0600 and run every hour, Monday - Friday
-- ---------------------------------------------------------
dbms_job.submit(
:jobno,
'BEGIN statspack_alert_proc; END;',
trunc(sysdate+1)+6/24,
trunc(
  least(
   next_day(SYSDATE - 1,'MONDAY'),
   next_day(SYSDATE - 1,'TUESDAY'),
   next_day(SYSDATE - 1,'WEDNESDAY'),
   next_day(SYSDATE - 1,'THURSDAY'),
   next_day(SYSDATE - 1,'FRIDAY')
)
+1/24,'HH')',
TRUE,
:instno);

commit;
end;
/
 

Way back in Oracle 7, database jobs were added. Jobs were background processes run by Oracle to perform scheduled tasks. Back then, the idea was that the dbms_job processes were permitted via the job_queue_processes init.ora parameter and were primarily for replication purposes; namely, snapshot refreshes. Over the next few major releases, dbms_job?s usage increased to include many additional purposes, basically to the point of serving as a generic job scheduler of sorts for many different kinds of Oracle jobs.

However, there are a number of shortcomings with the dbms_job facility like the fact that it cannot handle job dependencies. Thus, as of Oracle 10g, the dbms_job package has been superseded by the new dbms_scheduler package, which is covered in the next section, and the job_queue_processes parameter has been deprecated. In fact, Oracle recommends disabling dbms_job by revoking the package execution privilege for all users. Therefore, dbms_scheduler is truly the clear choice now.

However, for those on older versions of Oracle or who must still maintain systems built using dbms_job, examples of dbms_job package usage will be examined. The two most used procedures for this package are RUN and SUBMIT. Run forces a job to begin execution immediately, and submit permits one to schedule that job to run at some time in the future, with or without a next iteration repeat specification. The most challenging part, in terms of being least obvious, is specifying the next date and interval parameters, as shown here.

 

SQL> var job number

DECLARE

  X NUMBER;

BEGIN

  SYS.DBMS_JOB.SUBMIT

    (

      job        => :job

     ,what       => 'DBMS_STATS.GATHER_SCHEMA_STATS (''BERT'');'

     ,next_date  => to_date('07/03/2008 13:49:39','mm/dd/yyyy hh24:mi:ss')

     ,interval   => 'TRUNC(LAST_DAY(SYSDATE)) + 1 + 8/24 + 30/1440'

     ,no_parse   => FALSE

    );

END;

/

SQL> print job

PL/SQL procedure successfully completed.

 

 

       JOB

----------

        21

 

The next date simply had to be a valid date, but one had to remember that any time specification that was truncated (e.g. minus minutes and seconds) meant the same as all zeroes. So ?07/03/2008? without the 13:49:39 would actually mean midnight July 3rd. Likewise, the interval parameter was a calculation of the next date when the job would run, so it too had to be valid and was important down to the very same detailed level. Thus, next date = SYSDATE would mean run now, with an interval of SYDATE+1 meaning tomorrow at the same time as now, i.e. right now plus exactly 24 hours. If instead one wanted it run right now and then tomorrow at noon, the interval would be SYSDATE + 1 + 12/24 + 00/1440 where the 12/24 is for hours and the 00/1440 is for the minutes.

 

There are also three data dictionary views to check on these jobs: ALL_, DBA_ and USER_JOBS. So if the DBA wants to schedule running statistics on the BERT schema at 8:30 AM each day, here is the code to set and verify that it has been set.

 

SQL> select job, schema_user, last_date, next_date, interval, what from dba_jobs;

 

JOB SCHEMA_USER  LAST_DATE NEXT_DATE INTERVAL

---- ------------ --------- --------- ------------------------

WHAT

--------------------------------------------------------------

   1 SYSMAN       03-JUL-08 03-JUL-08 sysdate + 1 / (24 * 60)

EMD_MAINTENANCE.EXECUTE_EM_DBMS_JOB_PROCS();

 

  21 BERT                   03-JUL-08 TRUNC(LAST_DAY(SYSDATE))

                                       + 1 + 8/24 + 30/1440

DBMS_STATS.GATHER_SCHEMA_STATS ('BERT');

 

Finally, if one wanted to remove a job from the schedule, simply call the REMOVE procedure like this. To see what jobs are currently running, query the dba_jobs_running data dictionary view. Remember, it only shows the jobs actually currently running, so it may not return too many rows at any given time unless a ton of stuff has been scheduled.

 

SQL> execute dbms_job.remove(21);

 

PL/SQL procedure successfully completed.

 

SQL> select job, schema_user, last_date, next_date, interval, what from dba_jobs;

 

 JOB SCHEMA_USER  LAST_DATE NEXT_DATE INTERVAL

---- ------------ --------- --------- ------------------------

WHAT

--------------------------------------------------------------

   1 SYSMAN       03-JUL-08 03-JUL-08 sysdate + 1 / (24 * 60)

EMD_MAINTENANCE.EXECUTE_EM_DBMS_JOB_PROCS();

 

For more information on Oracle DBMS_JOB see the following links:




 

 

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