Understanding the application environment
For existing environments, the first step is to identify all components and understand how they relate to each other. The most important task is to understand the requirements and flow of the existing application(s) and what can or cannot be altered. The application is key to the scalability of any infrastructure, so a detailed understanding is mandatory to scale effectively. At a minimum, application analysis must include a breakdown of transaction types and volumes as well as a graphic view of the components in each tier.
Figure 2-1 can aid in determining where to focus scalability planning and tuning efforts. The figure shows the greatest latency for representative customers in three workload patterns, and which tier the effort should be concentrated on.
Figure 2-1 How latency varies based on workload pattern and tier
For example, for online banking, most of the latency typically occurs in the database server, whereas the appserver typically experiences the greatest latency for online shopping and trading sites.
The way applications manage traffic between tiers significantly affects the distribution of latencies between the tiers, which suggests that careful analysis of application architectures is an important part of this step and could lead to reduced resource utilization and faster response times. Collect metrics for each tier, and make user-behavior predictions for each change implemented. WebSphere offers facilities for monitoring the performance of an application.
As requirements are analyzed for a new application, strive to build scaling techniques into the infrastructure. Implementation of new applications offer the opportunity to consider each component type, such as open interfaces and new devices, the potential to achieve unprecedented transaction rates, and the ability to employ rapid application development practices. Each technique affects application design; similarly, application design impacts the effectiveness of the technique. To achieve proper scale, application design must consider potential scaling effects. An iterative, incremental approach will need to be followed in the absence of known workload patterns.
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IBM is a trademark of the IBM Corporation in the United States, other countries, or both.