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<== Date ==> <== Thread ==>

Subject: Re: EPICS alarming on VAL != X
From: "J. Lewis Muir" <[email protected]>
To: Jameson Graef Rollins <[email protected]>, [email protected]
Date: Wed, 23 Jul 2014 10:52:54 -0500
On 7/21/14, 1:11 PM, Jameson Graef Rollins wrote:
> On Mon, Jul 21 2014, Benjamin Franksen
> <[email protected]> wrote:
>> Why don't you just set DRVL=DRVH=<the desired value>. In that case
>> the record simply can't take on any other value. No need to even
>> think about alarms for situations that can never arise...
>
> Hi, Ben.  For the moment we want to be able to easily change the
> parameters if needed; we just also want a good way to track any
> changes.  The alarm system would be a good way to do that, if we could
> alarm on records not being at a particular set point.
>
> We have also looked at "locking" the parameters to their set point
> values by using the access security framework, but we're hoping to
> avoid that level of restriction for the time being.  Access security
> would I think be preferable to something like DRVL=DRVH=VAL, since it
> would provide feedback to our MEDM operators that the parameters are
> purposely locked in place.
>
> Thanks for the suggestions, though.  Others are welcome!

Hi, Jamie.

It sounds like you're kind of abusing the EPICS alarm subsystem.  Maybe
a better approach would be to keep the expected values of PVs in a
separate system that just monitors or polls the PVs and alerts you via
email or whatever when a value is different from expected.  You then
either update the expected value in the separate system to match the new
value (legitimate change) or you track down why the value was changed
and revert it (illegitimate change).

Lewis

References:
EPICS alarming on VAL != X Jameson Graef Rollins
Re: EPICS alarming on VAL != X Johnson, Andrew N.
Re: EPICS alarming on VAL != X Jameson Graef Rollins
Re: EPICS alarming on VAL != X Benjamin Franksen
Re: EPICS alarming on VAL != X Jameson Graef Rollins

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