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

Subject: Re: CA Priority for PV Gateway
From: Andrew Johnson <[email protected]>
To: "Ernest L. Williams Jr." <[email protected]>
Cc: Core-Talk <[email protected]>
Date: Tue, 21 Jul 2009 14:50:18 -0500
Hi Ernest,

On Tuesday 21 July 2009 11:29:37 Ernest L. Williams Jr. wrote:
>
> Shouldn't connection that the PV gateway has to IOCs be attached with a
> high CA Priority?

Not necessarily, that probably depends on the design of your control system.  
If you only have OPI connections coming through the gateway the current 
setting is probably right.

> How do we change this?

The priority of any CA channel connection is controlled by the client when it 
connects to the PV, so the gateway could request a higher priority for the 
channels on its client-side if it was coded to do so.  However both the calls 
to ca_create_channel() in the gateway code currently specify the fixed value 
CA_PRIORITY_DEFAULT for their priority.  Note that changing the priority of 
your clients can have undesirable effects within the IOCs though if you're 
not careful.

One quick way to raise the priority of your gateway channels would be to 
rebuild the gateway to use something like CA_PRIORITY_ARCHIVE instead, 
although this would then affect all PVs on all IOCs that the gateway connects 
to.

Better solutions might be to add a command-line argument to configure that 
fixed value (similar to the  -p <prio>  option Ralph recently added to the 
caget, caput, camonitor and cainfo programs in Base), or even to make it 
controllable through the gateway's configuration file on a per-channel 
(regexp) basis.

I believe CosyLab has experience in making changes to the gateway code if you 
don't have any effort available to do that in-house.

- Andrew
-- 
The best FOSS code is written to be read by other humans -- Harold Welte

Replies:
Re: CA Priority for PV Gateway Ralph Lange
RE: CA Priority for PV Gateway Jeff Hill

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