As the need for enterprise scalability is increasing, it challenged the traditional 2 tier architecture. In 1995, a new variant of 2 tier architecture came into existence where there was reduction in client-side headache. Such systems comprised of following three levels/tiers:
- User Interface Layer: This layer/tier comprised of functionality for simple GUI required for communication with database server and it runs on end-users computer. It sometimes performs a role of validating the input at users' side.
- Business Logic & Data Processing Layer: It acts as a middleware which runs on separate machine and whose responsibility is to handle business and application logic. Sometimes it is also known as "Application Server".
- Database Server: It stores the data required by middle layer. This layer may run on separate server known as database server whose primary job is to handle all database related requests from client side or through middle layer.
