Experimental Physics and
Industrial Control System

Matthieu Bec <[email protected]> · Tue, 15 Sep 2009 00:07:08 -0400

Hi,

That certainly is a good read (I think would deserve an entry in the

appdev guide or epics wiki)

independently of DBR_ type you use with channel access considerations

and I suspect other PCAS channels consideration that might be yet

another discussion:

does the pv crawler used for the IRMIS RDB let you differentiate:

instance_of_old_kind_xxx_record <that does not have a .YYY field>

instance_of_new_kind_xxx_record <that has the new .YYY field, but use

the default>

Matthieu

On 09/14/09 23:20, Don Dohan wrote:

The last cut and paste didn't make it:

Kay discusses the relationship between PVs, records and names at
http://www.aps.anl.gov/epics/tech-talk/2007/msg00853.php

Don

On 9/14/09 11:18 PM, "Don Dohan"<[email protected]>  wrote:

If you mean the pv crawler used for the IRMIS RDB, the crawler extracts and
stores both the record name and user defined field type instance values.  The
crawler maintains a link to the dbd file used in defining each record, making
it possible to reconstruct the full record using both user defined field
values and default field values.

PVs, however are still something a little different - see Kay Kasemir's
explanation

On 9/14/09 9:09 PM, "Matthieu Bec"<[email protected]>  wrote:

Hi all,

I'm having a terminology issue someone might help with, because the
comments posted on this thread appear to mix 'record' and 'PV'
terminology interchangeably. Most of the time it's clear, and although
there is a reasonable '1 to n' relation between the two, I can think of
example that relation can break. To give an example, say:

     ioc1 uses old xxx record type, that does not have .YYY field
     ioc2 uses new xxx record type, that has a new .YYY field

xxx 'record' (dbl/dbgrep etc) report the same thing.
but ioc2 use a newer version that might add/remove some fields (that I
think is what we really call PV = I think of it as the entity you get
over channel access)

So what does pvCrawl really look at: PVs or records? does it figure in
my example field .YYY exists in ioc2 but not ioc1?

Thanks
Matthieu

--
Matthieu Bec              Gemini Observatory
Tel: +56 51 205785        c/o AURA, Casilla 603
Fax: +56 51 205650        La Serena, Chile

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System