On Mon, 30 Oct 2000, Frank [iso-8859-1] J�rdens wrote:
> Maarten Boekhold wrote:
> > Openlink *does* allow you to download an evaluation copy of the multi-tier
> > Universal Data Access set (that's the only one that works on UNIX, the
> > single-tier editon is only available for windows platforms).
> >
> > Even if you use Openlink, you would need a separate driver manager. They
> > actually recommend iODBC.
>
> What does the multi-tier Universal Data Access set do exactly? Maybe I'm
> still unclear about the term multi-tier. For instance, when I use the
> Win32 PostgreSQL ODBC driver from my NT box to access the PostgreSQL
> server on my Linux computer, is this not already 2-tier (because it
> involves a client and a server on physically distinct computers)? Or is
> it single tier (because physically distinctness has nothing to do with
> it, and the setup just involves a straightforward client-server model
> with the ODBC driver/driver manager to mediate between client and
> server)?
Single tier has nothing to do with the number of computers invovled, but
the number of software components. A direct connection from the client to
the server is a single tier setup. It is how most systems work. If the
client connects to a middle tier system, which then connects to the
server, that is a two-tier system. More tiers aren't necessarily better,
unless the added complexity is actually providing you some functionality.
Now, the Openlink multitier system is designed to solve connectivity
issues. For instance, you don't have a native driver for your client. So
you use a Openlink client driver to connect to the Openlink broker which
passes database calls into a native client. This means that the broker
needs to run on a platform that a native driver is available for.
Tom