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Subject: Re: What will "ACKT=NO" do?
From: Andrew Johnson <anj@aps.anl.gov>
To: tech-talk@aps.anl.gov
Cc: "Zhang, Dehong" <dhzhang@slac.stanford.edu>
Date: Mon, 26 Mar 2012 14:11:27 -0600
Hi Dehong,

On 2012-03-26 Zhang, Dehong wrote:
> One of my records reads from hardware then triggers a chain of actions
> through FLNK.  From time to time it can get stuck: SEVR=INVALID,
> STAT=SCAN.  When it gets into this problem, it stops the FLNKing --
> which is the desired behavior, but stops forever.
> 
> Now, when next scan is due, I would like the record to forget about
> the previous problem, and try again.  If it can read (SCAN the streamdevice
> input), do everything as usual; if it fails, do not FLNK -- stop the
> chain, just forget about this cycle.
> 
> Will this "ACKT=NO" do the trick?  Please help to confirm.

No, ACKT just controls whether the record needs to have transient alarms 
acknowledged through the alarm handler or not, it has no effect on the IOC 
processing.  If a record that has ACKT=YES goes out of alarm state before the 
operators have acknowledged that alarm then they will still have to do so for 
the alarm to be cleared on the ALH screen, but if ACKT=NO then unacknowledged 
alarm from this record will disappear from the ALH screen as soon as the alarm 
condition is removed.

The SCAN/INVALID alarm you are seeing is raised when the IOC tries to process 
a record and finds the PACT field has been true for the last 10 tries.  The 
fact that you're getting these suggests that your database design should be 
improved to prevent this happening.  You would have to describe the current 
processing chain for us to help you with that though.

- Andrew
-- 
Never interrupt your enemy when he is making a mistake.
-- Napoleon Bonaparte

References:
What will "ACKT=NO" do? Zhang, Dehong

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