In the mid-1990s, as applications became more complex and potentially could be deployed to hundreds or thousands of end-users, the client side of this architecture gave rise to two problems:
•A ‘fat’ client, requiring considerable resources on the client’s computer to run effectively (resources include disk space, RAM, and CPU power).
•A significant client side administration overhead.
By 1995, a new variation of the traditional two-tier client-server model appeared to solve these problems called the three-tier client-server architecture. This new architecture proposed three layers, each potentially running on a different platform:
(1)The user interface layer, which runs on the end-user’s computer (the client).
(2)The business logic and data processing layer. This middle tier runs on a server and is often called the application server. One application server is designed to serve multiple clients.
(3)A DBMS, which stores the data required by the middle tier. This tier may run on a separate server called the database server.
The three-tier design has many advantages over the traditional two-tier design, such as:
•A ‘thin’ client, which requires less expensive hardware.
•Simplified application maintenance, as a result of centralizing the business logic for many end-users into a single application server. This eliminates the concerns of software distribution that are problematic in the traditional two-tier client-server architecture.
•Added modularity, which makes it easier to modify or replace one tier without affecting the other tiers.
•Easier load balancing, again as a result of separating the core business logic from the database functions. For example, a Transaction Processing Monitor (TPM) can be used to reduce the number of connections to the database server. (A TPM is a program that controls data transfer between clients and servers in order to provide a consistent environment for Online Transaction Processing (OLTP).)
kevowmuchiri answered the question on July 4, 2018 at 15:28
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