Schedule a job to run every second, how

We are on Workgrop Oracle server 7.3/NT 4.0.

I did the following to schedule a job to run for every second but it runs every minute instead. I changed the job_queue_interval values from the default 60 to 1 and restarted the server but did not seem to change anything. What happened? Thanks.

variable jobnum number
begin
  dbms_jo.submit(:jobnum,'insert into test values(1,sysdate);',

                  sysdate,'sysdate+1/86400');