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

Subject: Re: Events lost, discard count was XXX
From: hill@luke.atdiv.lanl.gov (Jeff Hill)
To: csuka@desy.de, tech-talk@epics.aps.anl.gov
Date: Fri, 1 Mar 96 10:03:18 MST
Gabor,

> 
> I have see the following on my IOC console:
> 
> --
> -> 0xd89d60 (CA event): Events lost, discard count was 1646
> 0xd89d60 (CA event): Events lost, discard count was 1774
> 0xd89d60 (CA event): Events lost, discard count was 2


This occurs when a client is consistently consuming 
less events per sec than the server is generating per sec.
There is enough buffering in the system so that
the client can briefly fall behind. However, if this condition is
sustained then the server will eventually discard events
for the client involved (other clients are not effected).

Possible causes (a particular type of client involved):
o client is synchronizing a slow activity with every event

	Some OPI client side tools avoid these problems by implementing
	a cache with an associated modified data tag for each
	PV that is monitored. CA event call back functions
	update this cache instead of performing the slow activity 
	directly (ie drawing on the screen etc).

Possible causes (a particular host involved):
o client isnt given enough CPU 

Possible causes (a particular network involved):
o events cant be communicated over the network as fast as the server 
is generating them. A network path to the client might not exist
or it might be saturated.

Possible causes (most clients involved):
o scan rates for the records involved are too high (frequent)
o deadbands need to be set for the records involved


Jeff

______________________________________________________________________
Jeffrey O. Hill			Internet	johill@lanl.gov
LANL MS H820			Voice		505 665 1831
Los Alamos, NM 87545 USA 	FAX		505 665 5107


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