Page #113 (Chapter 11. Scalability)

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[oR]

Introduction

Scalability is defined as the measure of an application s resistance to performance degradations when it services multiple concurrent requests. A perfectly scalable application would provide constant performance regardless of the number of concurrent users. However, such an application exists only in theory, as it requires infinite resources. In the real world, it is very common for two applications to contend for a shared resource such as memory, database access, or CPU time. In this case, one application has to wait until the other is finished using the resource, resulting in degraded performance.

There are several ways to resolve this problem, including the following:

• Increase the supply of available resources (more processors, memory, database handles, etc.)

• Design the application so that each request uses shared resources as efficiently as possible.

For the greatest degree of scalability, the developers may end up doing both.

While the first method requires a hardware or software upgrade to the system, the second method can be achieved programmatically.

Let s look at some COM+ services that help us achieve the second option.

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