Hi,

Yes, indeed that seems to be the most logical solution.

However -
Before I joined my company and wrote the conduit for them, they used
Appforge's Universal Conduit.
This is a conduit written by Appforge (I think they were purchased by
Oracle) that creates a mirror of an Access database (well, any database that
can be DSN'ed into the system, actually) onto a Palm device.
And that conduit worked fantastic -

   1. If no changes were made to either side, the synchronization will
   not take any time at all
   2. If changes were made, only the affected records will be sync'ed.
   3. If changes were made to the same record on both sides, the changes
   will be merged, so no data is lost.

All of these were accomplished excellently without manually embedding a
dirty bit.
The third bullet above indicates that there is more than just a dirty bit
set - it keeps track of every field, not just every record. Sort of a dirty
bit for each field, if you will.

So I'm assuming Appforge found a way to track after the data cleverly enough
to make synchronizations fast and accurate, without having to modify the
existing database, or rely on a stronger database engine than Access.

My bet is that they make a copy of the database each time it is sync'ed.
Then, on the next sync, they have 3 versions for each record - the PC's, the
Palm's, and the record that was saved after the last sync. That way they
know which fields were changed on each side.
I tried to do the same thing -
I made a copy of my MDB file, and used the linked tables option to link my
two MDB files. So now I have two versions for each table - the current table
and the table that will be saved after each sync.
But now I'm stuck because I can't think of a fast enough SELECT clause that
will pull only the modified records out of the current table.
If Access supported the "EXCEPT" SQL operator (
http://msdn2.microsoft.com/en-us/library/ms188055.aspx), it could be done
using the following simple query:

SELECT * FROM tblCurrentTable
EXCEPT
SELECT * FROM tblLastSyncTable

Does anybody have any better ideas?
I really don't want to start adding dirty bits to all my tables, and I want
a much more elegant and generic solution to the problem.

If you're wondering why I'm not just using Appforge's solution, the answer
is that they only support creating a mirror between the Access database and
the palm database. I had to write a conduit that synchronizes only part of
the "big" Access database to the "small" palm database.

Thanks

2008/2/12, epankoke@comc... <epankoke@comc...>:
>
> I worked on a project once that used an Access Database, and what we did
> was create our own "dirty" flag at the end of the record.  Basically, a one
> byte flag that was 0 for unchanged and 1 for changed (we actually had a more
> complex setup, but this would be the basic route to take).  Then all you
> have to look at on the Access side is the recordset where DirtyFlag = 1.
>
> --
> Eric Pankoke
> Founder / Lead Developer
> Point Of Light Software
> http://www.polsoftware.com/
>
>

--
For information on using the ACCESS Developer Forums, or to unsubscribe, please see http://www.access-company.com/developers/forums/