schedule a job every 15 mins *but* only during the office hours

Hi all,

I'm trying to setup snapshots to run every 15 minutes during working hours,
else hourly.  I'm ignoring weekends for now,...

Origonally I tried:

var job number;
begin
 sys.dbms_job.submit(
  job => :job,
    what => 'statspack.snap();',
    next_date => trunc(sysdate,'HH24') + 1/24,
    interval => case
          when (to_char(sysdate,'hh24') between 8 and 20) then
           'trunc(sysdate,''MI'') + 15/1440' -- 15 mins
          else
           'trunc(sysdate,''HH24'') + 1/24'
        end
 );
  commit;
end;
/

but it seems that interval will only be set once, i.e. when the dbms_job is 
actually submitted.
And not each "run", the evaluation of the case statement is stored and not the 
statement
its self.

I then tried using a function instead of sql, one which returned a date string 
for the next time to 
run.  But it is only evaluated the once as above.

I tried a similar approach with next_date, but got syntax errors.

Can it be done this way?  I've written a work-round using a wrapper for snap():
I schedule procedure every 15 min and it works out whether it should call a 
snap or not:

CREATE OR REPLACE PROCEDURE snapIf(
 p_now date default sysdate,
 p_startOfDay_HH24 number default 8,
 p_endOfDay_HH24 number default 17, -- includes 17:59
 p_startOfWeekD number default 2, -- Monday
 p_endOfWeekD number default 6 -- Friday
 ) is
begin
  if (to_char(p_now,'HH24') between p_startOfDay_HH24 and p_endOfDay_HH24)
  and (to_char(p_now,'D') between p_startOfWeekD and p_endOfWeekD)
  then
      --dbms_output.put_line('snap during week');
      statspack.snap();
  elsif to_char(p_now,'MI') = 0 -- on the hour outside office hours
  then
      --dbms_output.put_line('snap on the hour');
      statspack.snap();
  else
      --dbms_output.put_line('no snap');
      null;
  end if;
end;

Any thoughts...

Cheers
Tony

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