NonStop Systems Introduction

The Application Server Environment
NonStop Systems Introduction— 527825-001
3-8
Multi-Tiered Architectures
N-tiered architectures have all of the advantages of two-tiered architectures and also
allow:
•
Easier replacement or addition of GUI interfaces because the data capture is
separated from the transaction management functions
•
Consolidation of transaction processing management functions in a host computer
while retaining access to legacy applications and databases through a different
host computer
•
More modular application programs for easier maintenance
•
Easier geographic distribution of databases when that is needed
In a three-tiered or N-tiered architecture, tiers 2 and 3 can also reside within a single
host computer. The logical distribution of functions is more important than the physical
distribution of functions.
The application server software enables programs to execute efficiently in a
client/server architecture. The application server components make it possible to
separate the business logic from platform-related code and to run the separate
modules of code on separate computers. The application server handles all of the
internal housekeeping tasks, including internal logic and connectivity, required by
client/server applications.
Figure 3-5 on page 3-9 shows another example of an N-tiered architecture. This
example includes:
•
Clients consisting of a Java application and a web browser running on a PC. This
constitutes the client-side presentation layer.
•
Server-side presentation logic running on a separate web server. These are the
web components of the application, and often consist of Java Servlets or
JavaServer Pages.
•
The business logic and database access components running on a NonStop
server. The business logic is composed of business objects, such as Enterprise
JavaBeans.