Trigger which fire on a specific time ?

Question

Hello expert,
my requirement is to automatically cancel requisition's which are older than 3 day's.
for this i have to create some trigger. i created a trigger on database startup , but if i do not restart my server than
it will not work.
i also have create dml trigger but may be it will fire unnecessarily. so suggest me some process which check on some specific time in database
and cancel the requisition.
Thanks
yash

Answer 1

>
i create procedure and create a job by scheduler. and its working.
but i did not understand the dbms_scheduler.create_schedule .
i used dbms_scheduler.create_job to create a job with procedure to called.
but how to attach procedure with dbms_scheduler.create_schedule ???
>
You don't need to. You can just specify the repeat_interval like the example in the link shows
BEGIN
  DBMS_SCHEDULER.create_job (
    job_name        => 'test_full_job_definition',
    job_type        => 'PLSQL_BLOCK',
    job_action      => 'BEGIN my_job_procedure; END;',
    start_date      => SYSTIMESTAMP,
    repeat_interval => 'freq=hourly; byminute=0; bysecond=0;',
    end_date        => NULL,
    enabled         => TRUE,
    comments        => 'Job defined entirely by the CREATE JOB procedure.');
END;
/That example shows that the job will run every hour on the hour. You need to decide how often your job and procedure should run. The procedure should check for cancellations.
You also need to start revisiting your previous 155 (81 unresolved) threads and mark them ANSWERED as appropriate.