In three-tier client/server, the processing is divided between two or more servers, one typically used for
application processing and another for database processing.This is common in large enterprises.
It decomposes an application into three sets of services: UI, business, and data. In this architecture UI resides in
Client, business logic resides in business logic server and data in database server.
A three-tier architecture introduces a server (or an "agent") between the client and the server. The role of the
agent is manifold.It can provide translation services (as in adapting a legacy application on a mainframe to a
client/server environment), metering services (as in acting as a transaction monitor to limit the number of
simultaneous requests to a given server), or intelligent agent services (as in mapping a request to a number of
different servers, collating the results, and returning a single response to the client).
