Very simple question about DBMS_SCHEDULER jobs

Question

Hi,
I have a scheduled job and its repeat interval is every 30 min for all hours.
And also assume that my job is started at 11 am but it couldnt be completed till 11.30 am and it is finished at 11.45 am.
What will be the scheduled execution on 11.30 am? It will start just after previous one finished?

Answer 1

Create a table for testing:
SQL> create table scheduler (starttime date, endtime date);
Table created.
SQL>
Create a testing procedure:
SQL> !cat wait_a_while.sql
create or replace procedure wait_a_while(waittime IN int)as
  l_starttime date;
begin
  select sysdate into l_starttime from dual;
  insert into scheduler (starttime) values(l_starttime);
  dbms_lock.sleep(waittime);
  update scheduler set endtime =(select sysdate from dual) where starttime=l_starttime;
  commit;
end;
SQL>
Schedule a job every minute:
begin
   dbms_scheduler.create_job(job_name=>'wait_a_while_job',
                             job_type=>'PLSQL_BLOCK',
                             job_action=>'begin
                                            martijn.wait_a_while(120);
                                          end;',
                             start_date=>sysdate+1/(24*60),
                             repeat_interval=>'FREQ=minutely;interval=1');
   dbms_scheduler.enable('wait_a_while_job');
   commit;
end;
Let this go for a while, and query the table:
SQL> select * from scheduler order by starttime;
STARTTIME            ENDTIME
2013-DEC-14 14:59:59 2013-DEC-14 15:00:02
2013-DEC-14 15:00:24 2013-DEC-14 15:01:24
2013-DEC-14 15:33:09 2013-DEC-14 15:33:10
2013-DEC-14 15:36:40 2013-DEC-14 15:38:40
2013-DEC-14 15:38:40 2013-DEC-14 15:40:40
2013-DEC-14 15:40:40 2013-DEC-14 15:42:40
2013-DEC-14 15:42:40 2013-DEC-14 15:44:40
2013-DEC-14 15:44:40 2013-DEC-14 15:46:40
8 rows selected.
SQL>
So.....play around a little.
But I would say that the next job waits until the first job finished.