How to schedule jobs in Oracle Database

Introduction

We often wants to run pre-defined jobs at different schedule. Oracle database provides dba_jobs/dbms_scheduler (Oracle Database job scheduler) for the scheduling of pre-defined jobs.

Information about DBA_JOBS ( Till 9i)

Query to see the jobs running through dba_jobs

select /*+ rule */ * from dba_jobs_running;

or

select /*+ ordered */ * from dba_jobs_running;

Common Reason why jobs don’t execute automatically and as scheduled
(1) select instance_name,logins from v$instance;
If the logins=RESTRICTED, then:
alter system disable restricted session;

(2) check the JOB_QUEUE_PROCESSES
show parameter JOB_QUEUE_PROCESSES
It should greater then 0

(3)Is the job BROKEN?
select job,broken from dba_jobs where job=&1;
If broken, then check the alert log and trace files to diagnose the issue

(4) _SYSTEM_TRIG_ENABLED=FALSE
Check if _system_enabled_trigger=false
col parameter format a25
col value format a15
select a.ksppinm parameter,b.ksppstvl value from x$ksppi a,x$ksppcv b
Where a.indx=b.indx and ksppinm=’_system_trig_enabled’;

Information about DBA_SCHEDULER(With 10g and above)

With Oracle 10g ,dbms_job has been replaced dbms_scheduler .The Scheduler offers far more functionality than the DBMS_JOB package, which was the previous Oracle Database job scheduler.Oracle recommend changing all the jobs from DBA_JOBS to DBA_SCHEDULER from 10g onwards

— Old using dbms_job scheduler.

VARIABLE jobno NUMBER;
 BEGINDBMS_JOB.SUBMIT(:jobno, 'INSERT INTO empl VALUES (111, ''TECH'',''CAT'', ''[email protected]'', NULL, SYSDATE, ''AD_PRES'', NULL,NULL, NULL, NULL);', SYSDATE, 'SYSDATE+1');
 COMMIT;
 END;
 /
 PRINT l_job

New with dbms_scheduler scheduler.

BEGIN
 DBMS_SCHEDULER.CREATE_JOB(
 job_name          =>  'job1', 
 job_type          =>  'PLSQL_BLOCK',
 job_action        =>  'INSERT INTO empl VALUES (111, ''TECH'',''CAT'', ''[email protected]'', NULL, SYSDATE, ''AD_PRES'', NULL,NULL, NULL, NULL);
 start_date        =>  SYSDATE,
 repeat_interval   =>  'FREQ = DAILY; INTERVAL = 1');
 END;
 /

We can find job information by running the below queries

select 
 job_name,
 enabled
 from
 user_scheduler_jobs;

 select
 job_id,
 freq_type,
 freq_interval,
 freq_subday_type,
 freq_subday_interval, 
 freq_relative_interval,
 freq_recurrence_factor,
 active_start_date,
 active_end_date,
 active_start_time,
 active_end_time,
 schedule_id
 from
 dba_scheduler_jobs;

 SELECT owner, job_name, enabled FROM dba_scheduler_jobs; 

The job created above can be dropped using the below command

BEGIN
   DBMS_SCHEDULER.drop_job (job_name => 'job1');
 END;
 /

The above is very simple use of DBMS_SCHEDULER. DBMS_SCHEDULER has lot of other features also like create program , create schedule which then can then use to create the Jobs for scheduling