Oracle Scheduler Postponed job

前面的例子中，可以使用plsql语法指定repeat_interval
repeat_interval => 'sysdate + interval ''10'' second'

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在 指定时间，前一个instance还在运行的情况下，会发生什么？
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被 执行的sp随机停止8-12秒( p_2使用了dbms_lock，这个必须有权限)
grant execute on dbms_lock to xxx;
create or replace procedure p_2 is
  l_c integer;
begin
  select trunc(dbms_random.value(8,12)) into l_c from dual;
  insert into scheduler_test(x,y) values(to_char(sysdate,'yyyymmdd hh24:mi:ss'),l_c);
  commit;
  sys.dbms_lock.sleep(l_c);
end;
/

每10 秒的整点运行一次
declare
  l_x integer := 0;
begin
  dbms_scheduler.create_job(job_name        => 'ttt',
                            job_type    => 'stored_procedure',
                            job_action => 'p_2',
                            start_date      => systimestamp,
                            repeat_interval => 'freq=minutely;interval=1;bysecond=0,10,20,30,40,50');

  dbms_scheduler.enable('ttt');
end;
/

SQL> col x for a20
SQL> col y for a5
SQL> select * from scheduler_test order by 1;
 
X                        Y
-------------------- -----
20070802 10:40:40       10
20070802 10:40:50       10
20070802 10:41:01       10
20070802 10:41:11        8
20070802 10:41:20        9
20070802 10:41:30        9
20070802 10:41:40       10
20070802 10:41:50       11

从 结果分析看出，job会被延迟执行。如上面第3条应该在0秒执行，但是被延迟到01秒