by Harshal Morpari » Wed, 12 Mar 1997 04:00:00
Hi there,
I need some help.
We are making a model of a 3-tier client server architecture
with a thin VB (Win95) client, thick Unix, C++ application
server and a Unix-Sybase 10 database server. We have no clue
about how these components will integrate. If anybody can help
or has any documentation on this architecture or other 3-tier
architecture implementations or knows web sites with such info,
appreciated.
Bye.
Thanks.
by Bruce Tobi » Thu, 13 Mar 1997 04:00:00
> Hi there,
> I need some help.
> We are making a model of a 3-tier client server architecture
> with a thin VB (Win95) client, thick Unix, C++ application
> server and a Unix-Sybase 10 database server. We have no clue
> about how these components will integrate.
1. Remote OLE. VB has built-in support for this. The Unix side
is a bit trickier, but there are several alternatives.
a. SCO has a Unix Remote OLE implementation that runs on
most Unix servers (HP, Sun, IBM etc). See
http://www.vision.sco.com/news/sole/
b. Open Environment has a product called OLEEnterprise that
implements a version of remote OLE via TCP/IP. See
http://www.openenv.com
c. Software AG has released remote OLE implementations for
several Unix platforms. See
http://www.sagus.com/Prod-i~1/net-comp/dcom/index.htm
d. Sybase announced OLE middleware called ObjectConnect
a while back; I don't know what they've done with it,
though.
A warning: remote OLE can be slow. Benchmark early and often
if you plan to go this route.
2. Remote Procedure Calls. There are lots of products on the
market to facilitate this; perhaps the best-known is
EZ-RPC from NobleNet (which seems to have changed its name
to NobleNet RPC). See
http://www.noblenet.com
3. Plain old sockets. The roll-your-own approach. You can call
the winsock API directly from VB, or use a library or OCX
available from several vendors. On the Unix side there's
a lot of free example C++ source available. See, e.g.
http://w3imagis.imag.fr/Membres/Stephane.Riviere/doc/libc++.faq
4. Some of the freely-available C++ sockets libraries have
reached very high levels of sophistication, in particular the
ACE (Adaptive Communication Environment) toolkit. I don't
think that a VB interface has been written, but it might
be a worthwhile project. See
http://www.cs.wustl.edu/~schmidt/ACE.html
What would I recommend? Well, I'd probably recommend
re-evaluating your proposed architecture. Each of these proposed
architectures has its drawbacks, and any of them have the
potential to turn a six-week project into a six-month project.
What application requiremnts are driving your decision to
put a Unix/C++ application server in the middle?
by Vance Pa » Sun, 16 Mar 1997 04:00:00
> We are making a model of a 3-tier client server architecture
> with a thin VB (Win95) client, thick Unix, C++ application
> server and a Unix-Sybase 10 database server. We have no clue
> about how these components will integrate. If anybody can help
> or has any documentation on this architecture or other 3-tier
> architecture implementations or knows web sites with such info,
SimbaExpress is a good example for implementing such an architecture.
SimbaClient is installed on the clients to work as an universal ODBC
driver that talks to the middle tier, the SimbaExpress server. The
Express server contains the ODBC driver manager and will have various
ODBC drivers/communication libraries installed on it. The advantage of
this type of architecture is the ability to connect to different data
sources simultaneously. This 3-tier architecture is also scalable;
increasingly high levels of service causes only a linear decline in
performance.
Vance
---------------------------------------------------------
Free version of SimbaExpress! Download it at...
http://www.simbatech.com/express
Need to build ODBC drivers? Check out...
http://www.simbatech.com/sdk
---------------------------------------------------------
1. Designing 3-tier client/server architecture….
My employer wishes to design a large scale, 3-tier, client/server
application. The middle tier would be composed of CORBA objects,
factories, managers, in short business logic model. The 3rd tier will
be a database, and the client, well -- just the client.
My question is regarding the "business logic" (middle) tier which will
be written using CORBA. I have done some analysis and determined that
for any non-trivial middle tier one would need at least the following:
1. Naming service, to identify root objects and start of navigation
hierarchies
2. Relationship service to store relations between objects
3. Transaction service to promote data integrity between object
Other than the Naming and Event services, I am not sure if the
Relationship service or Transaction service exist for any of the ORBs
yet.
Have any one put together a non trivial business logic model using
CORBA? How did you solve the issues of relations, transactions,
persistency, between your objects?
Once such a dynamic model is put together how do I make sure that the
client stays synchronized with the data at the server(s). I guess I
could use the Observer pattern, but a number of people have advised
against using call back mechanisms in a large scale application. Are
there other techniques that can be used to keep the client always
up-to-date with the latest "picture" on the server?
Are there any conferences, or sources where I can find out some
techniques that people use to put together middle tiers? Are there
any case studies published describing what people have done, and how
it worked out for them?
Thanks for your help.
-AP_
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