looking for Cyrus mail format documentation

[John Alton Tamplin]

Henrique de Moraes Holschuh wrote:

>On Tue, 04 Feb 2003, Phil Howard wrote:
>  
>
>>I wonder how well that method of replication works when both nodes
>>cannot reach each other, and both are doing updates.  And I wonder
>>    
>>
>They don't.  If they cannot reach each other, at most one of them must allow
>updates.
>  
>
Which, as far as I know, is how all commercial databases also do 
replication.  Only those servers involved in a quorum (even if it is 
because the primary is treated as having more weight) can accept updates 
-- the other replicas can only be read-only.  Trying to allow arbitrary 
updates during disconnected operation and then merge the results into a 
consistent and deterministic state is not just hard, but impossible. 
 For example, if you allow flags to be set differently on the same 
message on each node, there is no way to resolve the two updates without 
discarding at least some of the work of one of the sessions. If you 
carefully constrain the updates that can be performed during 
disconnected operation (and for consistency that means even not in 
disconnected operation), then you can transform the problem from 
impossible to merely extremely difficult.

-- 
John A. Tamplin                               Unix System Administrator
Emory University, School of Public Health     +1 404/727-9931