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

Subject: Re: RE: PV's element count differs though CA gateway
From: Carl Schumann <schumann@fnal.gov>
To: Jeff Hill <johill@lanl.gov>, tech-talk@aps.anl.gov, "'Dehong Zhang'" <dhzhang@fnal.gov>
Cc: "'Salah J Chaurize'" <chaurize@fnal.gov>, "'Denise S. Finstrom'" <dfinstrom@fnal.gov>
Date: Tue, 25 May 2010 10:53:41 -0500
Hi,

It turns out the IOC changes the element count on the PV dynamically, so rebooting would present some issues:
1. The required frequency and determining when one is required.   The element count appears to be the product of two PV's values which may be changed by users at any time.
2. Disruption to other connections.   What does EPICS do if anything to reestablish connections when a machine along the connection is rebooted?

Thanks,
Carl

----- Original Message -----
From: Jeff Hill <johill@lanl.gov>
Date: Friday, May 21, 2010 3:30 pm
Subject: RE: PV's element count differs though CA gateway
To: 'Carl Schumann' <schumann@fnal.gov>, tech-talk@aps.anl.gov, 'Dehong Zhang' <dhzhang@fnal.gov>
Cc: 'Salah J Chaurize' <chaurize@fnal.gov>, "'Denise S. Finstrom'" <dfinstrom@fnal.gov>


> Hi Carl,
> 
> I suspect that the gateway has been attached to that PV for a long 
> time, and
> that it learned a maximum element count when it initially connected 
> which is
> no longer accurate. Rebooting the IOC or restarting the gateway, whichever
> is easiest, might help. Also, note that services (a waveform record in 
> an
> IOC in this case presumably) generally report a maximum element count 
> when
> the client connects, but can choose to return a lesser current amount 
> of
> elements later as appropriate. 
> 
> PS: I am out the door on the way to Oxford for the codeathon Saturday
> afternoon, and since the rules here say that I can't take my smart 
> card out
> of country then I will not have email access for some weeks after 
> that, but
> perhaps I will see you at the EPICS meeting.
> 
> Jeff
> ______________________________________________________
> Jeffrey O. Hill           Email        johill@lanl.gov
> LANL MS H820              Voice        505 665 1831
> Los Alamos NM 87545 USA   FAX          505 665 5107
> 
> Message content: TSPA
> 
> 
> > -----Original Message-----
> > From: tech-talk-bounces@aps.anl.gov [mailto:tech-talk-
> > bounces@aps.anl.gov] On Behalf Of Carl Schumann
> > Sent: Friday, May 21, 2010 1:15 PM
> > To: tech-talk@aps.anl.gov; Dehong Zhang
> > Cc: Salah J Chaurize; Denise S. Finstrom
> > Subject: PV's element count differs though CA gateway
> > 
> > Tech-talk, Dehong Zhang,
> > 
> > We have a client application which attempts to access a PV's 
> elements 0
> > to 999 .   This application is run on two sets of machines.   One set
> > must go through an EPICS gateway to access the PV.  The other set does
> > not do so.    The application does not run properly when going through
> > the gateway because of an out-of-bounds error at element 940.   It is
> > able to access elements all they way up to 999 without issue when there
> > is no gateway involved.
> > 
> > We were able to track this issue down to a difference in the element
> > count reported by the originating IOC vs. the gateway using cainfo.
> > For the gateway case cainfo reports element count 940, but for the
> > non-gateway case cainfo reports 1000.    Using EPICS_CA_ADDR_LIST we
> > were able to reproduce both element counts on a single machine depending
> > on whether the gateway or the originating IOC responded.   The 
> result is
> > attached.
> > 
> > Me and my co-workers find this result unexpected and are not sure 
> how to
> > fix it.   Any help would be appreciated please.  Thanks for your time.
> > 
> > Sincerely,
> > Carl Schumann
> > 
> > P.S.: for my co-worker Dehong owner of the hins_ws.py:
> > The client is hins_ws.py.   The PV is PD_LEBT:Inst:WS1.RST1.   It is 
> the
> > out-of-bound error that prevents the Save Result button from generating
> > a file.   Do have any insight about what might be going on here?  Thanks.
> 
>


Replies:
Re: PV's element count differs though CA gateway Dirk Zimoch
References:
PV's element count differs though CA gateway Carl Schumann
RE: PV's element count differs though CA gateway Jeff Hill

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