[AccessD] Manual Database Synchronisation

Are you going to use local PC's time/date? If so will you have to maintain
the correct date/time on all these machines? I have heard horror stories of
machines with incorrect dates wrecking havoc on DB update schemes.
Jim Hale 

-----Original Message-----
From: Joshua B [mailto:jbusergroups at optushome.com.au]
Sent: Tuesday, May 13, 2003 5:16 AM
To: accessd at databaseadvisors.com
Subject: [AccessD] Manual Database Synchronisation


Group:

Hoping someone may have a few ideas on this. I am in the process of setting
up specifications for the modification of a clients database. The client has
offices in five different locations around the world, and a database that
has been shared up until now using Access's in-built replication tool. At
the end of each trading day, the database would be sent to the other
offices, and they would synchronise. The db has now grown to the size where
this is not possible anymore (It weighs in at around 5 megabytes zipped up,
and the offices that don't have the luxury of cable are starting to
complain). They wish to send only the new and updated records back and
forth.

Eventually they will be looking at a web-based solution, but this will not
be happening for at least a year, if not more.

My idea is to time-stamp each record when it is updated (or added), and then
use this time stamp to determine which records need to be sent to the other
offices. I have been assured that the offices will "never" (I know that
thats a dirty word) be working on the same record on the same day, so there
will be no need to update on a field-by-field basis, I'll simply overwrite
the whole record with the updated information.

In the meantime, my main concern with setting this up is how I handle the
primary keys for records. Up until now, I have been a firm believer in using
an autonumber for a primary key. Of course, this will not be possible in
this scenario. When a record is added to the system and sent to all the
other offices, the primary keys will have to match, so that my code will be
able to match up the updated records when imported at the other end. The
best idea I have come up with is to use a random autonumber, and attach a
time-stamp to the end of that, and use it as a primary key. For there to be
a conflict, it would mean that two offices have generated a duplicate random
autonumber at the exact same second. I'm quite happy with the odds of that
never happening.

I just thought I would throw this in there, with the hope that maybe someone
has done something similar in the past. And of course, there is the likely
possibility that I am missing some incredibly easy way of doing this.

Thanks for reading :-)

Best regards.				 
Joshua B
jbusergroups at optushome.com.au
2003-05-13



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