Subject: Re: more proposed protocol changes

From: "David Chadwick" <[email-masked]>
Date: Thu, 3 Aug 2000 13:38:55 +0100

Date sent:      	Mon, 31 Jul 2000 17:05:30 -0700
From:           	Zachary Amsden <[email-masked]>
Subject:        	more proposed protocol changes
To:             	[email-masked]

> To accomodate simultanaeous LDUP partial updates to
> the same replica, it would make sense to allow the sender to
> optionally send an update vector containing describing the
> CSNs it is about to send.  This could be passed back to other
> suppliers for the same replica in the startReplicationResponse
> while the original replication is proceeding. 

Zachary

I worry about this sort of procedure, since the consumer is saying 
to the other suppliers that it has received the updates (from the first 
supplier) before it actually has. Once these suppliers store that 
update vector they will never attempt to update the consumer with 
these updates. Worse than that, if the connection with the first 
supplier breaks, the consumer now does not have the updates it 
has told everyone (except the first supplier) that it does have. What 
if the first supplier replicates with say the third supplier and gets the 
update vector from it before it restarts it link to the consumer. The 
first will now think that the consumer has the updates, wont it?

David

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David Chadwick
IS Institute, University of Salford, Salford M5 4WT
Tel +44 161 295 5351  Fax +44 161 745 8169
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Home Page  http://www.salford.ac.uk/its024/chadwick.htm
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