Re: FE/BE Replication Question

On Fri, 30 Dec 2005 11:52:02 -0800, Debbie
<Debbie@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote:

>I was able to find out the exact topology. The clients are thin clients that
>access 3 seperate servers through terminal services. All processing is done
>on the servers and the screen shots are sent to the client. In thinking out
>load, there should be a FE and BE for each location. The BE would be a
>partial replica for that location. Am I on the right track?

Where are the servers located? Are they in the same physical location?
If not, the same advice applies as before -- if they are connected
directly via LAN, then direct synchronization is acceptable. If they
are connected via WAN, then direct synchronization is not advised.

BTW -- if they *are* in the same physical location and on the same
LAN, then you should not be using replication in the first place!
Based on that principle, I would guess that they are in different
locations, and connected via WAN, and are *not* suitable candidates
for direct synchronization. You should investigate using Indirect
Synchronization. It is more difficult to implement, but is much more
robust. Using direct synchronization over a WAN is a recipe for
database corruption.

Secondly, if you have multiple people logging onto a single server at
one time using Terminal Services, then each login should have its own
FE. I don't have personal experience with this configuration, but it
is often mentioned in the newsgroups.


>
>In terms of synchronization, based on your answer, I could have a button on
>the front end that would sychronize the back end to the design master. Is
>that true?

Close, but not exact. The Design Master should *not* play a role in
your day-to-day activities. Instead, you should create a new replica
in the "central" location and synchronize with that one. The DM is a
special case -- you "hide" it in a location that is accessible only to
you, the developer, and you use it for modifying the database design
as required. You synchronize with it periodically to prevent it from
becoming "stale". The default period when a replica becomes "stale"
and is unable to synchronize with other members of the replica set is
1000 days, but you should synchronize with it more often that that.
Synchronizing with the DM is normally done manually.

>
>Thanks, I think I'm almost there!
>Debbie
>
>As for synchronizing
>"Debbie" wrote:
>
>> Hello all,
>> My client has an old Access application where all objects including tables
>> are in one database. They are also using replication whereas they have a
>> design master on the server and several locations have partial replicas which
>> are stored on the server, all clients are thin clients. They also are using
>> user level security. That all works fine.
>>
>> Now, I have re-written the application and in doing so have split the
>> database and continued to use user level security. That's all fine.
>> However, we are unsure about how to use replication in this design scenario.
>> The design parameters are:
>> - the design master and replicas are stored on the server.
>> - All the locations must have partial replicas containing only their data.
>>
>> I have the following questions:
>> 1. In this scenario, I can create partial replicas on the backend database.
>> However, should I create replicas for the front end database for each
>> location? Can you create a replica of a front end containing all objects
>> except tables? I have tried this and I got an error message. I think I need
>> to because the application is written in ADO and there are provider
>> statements with a hard coded path statement that points to the back end
>> database.
>> 2. Is there a way to synchronize a back end database from the front end?
>> In the old application since all object were in the same database, it wasn't
>> an issue.
>>
>> Thanks so much, I did download the Replication FAQ paper but nothing seems
>> to address this particular scenario. Any ideas are appreciated. Thanks so
>> much,
>> Debbie

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