Experimental Physics and
Industrial Control System

Jeff Hill <[email protected]> · Fri, 10 Jan 1997 09:41:52 -0700

Marty Kraimer wrote:
> 
> This message discusses IOC CPU Priorities.
> 
> How about the following priorities, from highest to lowest.
> 
> IOCHIGH
> IOCMEDIUM
> CAHIGH
> IOCLOW
> CAMEDIUM
> CALOW
> CAUDP and CATCP
> BACKGROUND

I agree that the application developer may decide that some 
db scan activities are non-essential and therefore should 
be run at a lower priority than the CA server. However, when 
choosing to do this the application developer should
be well aware that under increasing client load that there
may be long or short periods of time when the BACKGROUND and 
also the possibly the IOCLOW scan activities will be disrupted.
The application developer could easily end up with a situation
where the operator is able to start a new screen but he gets
an old value for the io periodically scanned at IOCLOW
priority and ends up making an incorrect decision based on the
having an incorrect perception of the state of the plant.
Since there would be no warning that scan activities have been
disrupted then this appears to be a particularly dangerous
pit that we may be digging for the application developer to
fall into.

Just me be paranoid.

Jeff

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

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System