Re: Client Server Architecture versus Multi Tier Architecture

shubtech@xxxxxxxxx wrote:

I agree that if we were to decide to eliminate Citrix
server we will have to pretty much re architect the current
application.

indeed :)


Guillem, you asked me what our communication requirements are, let me
try to answer this, as far as our cuurent application majority of the
processing is done on the SQL Server after the processing is done we
send the result back to the clinet in most cases its certain values
that are sent back to the client to populate the fields in the client
screen in cases of reports we actually send result sets back to the
client which could be several thousands of rows depending on the
report. Let me know if that is what you meant by communication
requirement.

it's more or less in the same direction I meant :)

Based on what you have wroten in your posts and making some
assumptions, questions you should make your people would be:

- for reports, do we really need to send back the whole result sets or
could we generate the report in the server and just send back the
report?

- what protocol do I use to communicate client with database? Could I
use the same protocol to communicate client with mid-tier? Mid-tier
with database? Is there any faster protocol we could use?

- is our client app retrieving exactly what the user needs or too much?
There is a non-written "law" which says "if you retrieve more than 200
records to show the user then you are probably retrieving too much
records". A user usually will not look at everyone of those 200
records. Of course this 200-limit depends on each case.

I agree I am asking a very wide question and I dont
expect a yes or a no, but just a general idea to determine if we were
to eliminate Citrix server wouldnt a three tier architecture be the
solution?

it's one solution but surely not the only one. If you eliminate the
Citrix server you'll need to control somehow both the connections and
the load balancing, either by your mid-tier or by another sw.

OTOH, as Daniel suggests it could help to find the bottlenecks...


Guillem you also asked me about the software requirement, and the
requirement is our application will have to support users from
different parts of USA to access the aplication and right now it is
being done with the help of citrix servers and the users connect to
the citrix server and run our client server application but they do
not want to use Citrix server any longer.

IMHO your company should consider carefully if dropping the Citrix
server is a good idea, since as Daniel and Eduardo pointed out,
connection pooling and load balancing would then become an issue to
solve.


Our current software is a thick client witten in Delphi, if we were
to change the architecture what are the different software tools that
we need to look at for turning this thick client to thin client.

there are a lot of midware solutions out there. Just google for them.
Of course you can program it on your own.

.net
comes to my mind, however we would like to use something that could be
easily converted or do we pretty much have to scrap the existing
client side coding and start over.

not really. Your client-side app could preserve the same GUI (refining
it is an option). If you use a 3-tier architecture what you need to get
off the client is the database logic, which passes onto the mid-tier,
and you only add the communication capabilities with the mid-tier.


Finally, there were some article in the internet where it said client
server application is best suited for upto 100 users, is that correct?

IMHO it depends on the load and frequency of use of every client, but
it's a good limit, more or less.

And I was also curious if you guys had any ideas on if the number of
users increases what would be the best thing to do in client server
environment to make it better.

besides what the others suggested, maybe database mirroring could be an
option for you, but I can't really help in that regard.

Good luck,
--
Best regards :)

Guillem Vicens Meier
Dep. Informática Green Service S.A.
www.clubgreenoasis.com
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Contribute to the Indy Docs project: http://docs.indyproject.org
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