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

Subject: Re: CA question with two identical servers
From: Scott Baily <sbaily@lanl.gov>
To: "Goff, Steven J" <steven.j.goff@boeing.com>
Cc: "tech-talk@aps.anl.gov" <tech-talk@aps.anl.gov>
Date: Fri, 26 Jul 2013 15:44:19 -0600
On 7/26/2013 8:32 AM, Goff, Steven J wrote:
I would like to use one CA application or MEDM display that will connect
to two identical servers running the same PVs. I would like both servers
to receive the Channel Access ca_put at the same time. This might mean I
have to modify EPICS code for each server to receive the data
simultaneously.
Any ideas on how I would achieve this?

One question is why do you want to do this?
The redundant IOC software was originally used to run two IOCs each of which talks on the same bus (so only one controls hardware at a time). I modified the redundant IOC software, so it can be used to setup 2 IOCs that command redundant hardware. Info nodes can be used to choose which records are synced, so that command channels can be kept in sync, while readback channels respond to the state of the hardware. Joerg Penning at DESY maintains it, and he has my changes. In this case only one IOC (the master) will respond via channel access, but they communicate with each-other to stay in sync, and the slave will take over if the mast fails.

If you just want to send a put to two IOCs simultaneously, you could use different PV names on each IOC, and have a soft IOC with a third PV (that your CA application connects to) this record could cause a dfanout to send puts to both IOCs.
--
Scott Baily
AOT-IC, MS H820
Los Alamos National Laboratory
Los Alamos, NM 87545
ph: (505) 606-2260

References:
CA question with two identical servers Goff, Steven J

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