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

Subject: Re: wrong timestamps in monitors
From: Ralph Lange <Ralph.Lange@bessy.de>
To: EPICS Core Talk <core-talk@aps.anl.gov>
Date: Thu, 29 Jan 2009 15:42:12 +0100
Hi,

One more aspect of this issue: currently the record timestamp is put on all PVs that belong to the record, even though CA has no concept of a record that would match this relation.

So - why not put this on the list of possible work packages for the next codeathon?

Definitely something worth to be fixed, changing a behaviour that no one should rely on (does someone?), and there are ways to improve this that do not need a lot of changes in the code once we agree on how this should be handled.

What do you think?
Ralph


On 29.01.2009 14:46 Benjamin Franksen wrote:
Hi,

I think this is a known issue, it is at least as old as 3.13.9. EPICS posts CA events when a non-VAL fields get written to, and it does so independently of record support. There are two cases:

- If the field does not have the PP property, then the record is not processed as a result of the put, and the CA event is posted with the old timestamp.

- If the field /does/ have the PP property, then the record gets processed as a result of the put, which woudl update the record's timestamp, but processing comes /after/ EPICS base posts the event, thus the event has the wrong (old) timestamp.

It should be clear that this means one should /not/ trust the history of value changes as e.g. reported by the channel archiver (or simply the output of camonitor) whenever the PV in question references a non-VAL field. At least not w.r.t. the reported timestamps.

Is this going to be addressed any time soon?

Cheers
Ben


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