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

Subject: Re: applications that use channel access
From: [email protected] (Jeff Hill)
Date: Wed, 27 Apr 94 09:48:59 MDT
Hello All,

John Winans writes:

> 
> For those applications (like burt, and the device abstraction stuff Claude
> has been working on) that only want to know the value on a one-shot basis,
> I would think that getting the value on the connect would be more efficient
> than otherwise.
> 
> What is going to be the generally accepted way to do that sort of thing
> anyway?  Is there going to be some special kind of call for it?  Or are
> they going to actually going to build a connection and then close it again?
> 

Applications like "burt, and the device abstraction stuff 
Claude has been working on" will normally need to fetch values
from several channels on the same IOC. This implies that the 
virtual circuit setup overhead as a percentage of the total 
labor for N channel value fetch requests might often be
insignificant.

It is possible that connectionless get/put requests would be 
a useful addition to channel access. They would be an
efficient choice when a single batch of gets/puts needed to be 
performed infrequently to a single IOC. They would be a poor 
choice for high throughput, ordered delivery dependent, or IOC 
state change (monitor) driven applications. I will keep this 
under consideration for EPICS V4 CA.

This does not change my resolve to eliminate the connectionless 
get capability that can currently be combined with the CA request 
to create a virtual circuit as described in the original source of 
this thread of discussion. So far I have not received a response from 
anyone that is using it.


Jeff


______________________________________________________________________
Jeffrey O. Hill			Internet	[email protected]
LANL MS H820			Voice		505 665 1831
Los Alamos, NM USA 87545	FAX		505 665 5107

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