Note that Replication and Splitting are two ALTOGETHER different
techniques. They can be used together - you might need to
Replicate the backend of a split database (never the frontend) if
users not on the same network need to share the data.
It's not just that they *can* be used together. It's that they
*must* be used together. The reason for that is that Jet Replication
simply doesn't work in the long run for the Access project. It was
designed for pure Jet objects (tables and queries) and works
beautifullly with those. But for Access objects
(forms/reports/macros/modules), it causes problems and can easily
get so corrupted that you lose the entire project. The Jet
Replication White Papers all recommend using replication as a viable
method of pushing out front end updates, but they are wrong, as
you'll see if you look at the Jet 4 Replication FAQ, which
recommends against it. See (all on one line, unwrapped):
http://www.dfenton.com/DFA/Replication/index.php/Things_not_to_believ
e_in_the_MS_documentation
The problems with replicating front ends were exacerbated with the
release of Access 2000, where the entire Access project is stored as
a BLOB in a single system table (this is also the reason for the
switch to the monolithic save model, and the loss of individual
modified/dates for Access objects). If you consider that several
changes to objects in your front end are actually going to be
propagated as multiple edits to a single record, and those edits
have to be reconciled between the two sides of the synchronization
(properties like filters and so forth get saved, too, and will get
synched in both directions), you will see why this is dangerous.
The split architecture is the only viable architecture for a
replicated Access database.
Of course, I'd also say it's the only viable architecture for any
multi-user database, replicated or not.
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You would need to run Delete queries to delete the "old" data; I
haven't done enough replication to be certain how that would
interact with later synchronization. It sounds like you want to
keep only recent data on some replicas, and all historic data on
another replica (the "data master" let's call it...?);
If you delete data from one replica, it will be deleted from each
other replica that synchs with it, so, no, this can't be done.
There are two issues here:
1. restricting the data in a particular replica to the data
generated at that replica, AND
2. filtering that data to the recent data.
The former can be done with partial replicas, where you filter which
data goes into a particular replica. However, I see no point in
using partial replicas, because then you lose the backup redundancy
of having lots of spread-out replicas with all your data in them
(it's kind of like the issue you have with full, differential and
incremental backups in regular backup software -- the latter two
take up less space and are faster to write, but it's much harder to
recover when you need to restore data, since you have to work from a
whole bunch of backup sets). If you don't want the end users to see
anything but their own data, that's easy enough to implement in the
front end, filtering on whatever criteria brand their records as
belonging to them.
As to the second issue, the filtering can be done in the
application. Unless you're running up against the 2GB data limit,
there really is no issue with performance or storage space, even
with 100s of thousands of records. Yes, you'll need your data tables
appropriately indexed, but once that's done, data retrieval should
be blazingly fast in any context in which you're filtering the data
set presented to the user (in a form or a report).
I'm sure this can be done but
I'd want to pick MichKa's brain on just how! See if there is
discussion of the subject at
http://www.trigeminal.com, the mother
lode of replication information.
There is no way to restrict data in a replica by a changing piece of
criteria. Once the data is in the replica, it can't be removed
without it also being removed from all the other replicas that had
that data in them.
It really ought to be a complete non-issue if proper Jet user-level
security is put in place. If that's done, then all the restrictions
would be done in the application itself, and end users would have no
access to data that wasn't theirs.
