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7. In the Java Virtual Machine pane, under General Properties, in the Initial Heap Size field,
type the desired value of the initial heap size (in MB). If this is the first time that you are
changing this value, the field is blank. This indicates that the default value is used. See
Figure 8-13. Click OK.
Figure 8-13 Setting the initial heap size
8. Click the Save link at the top of the page to save your changes.
9. Log out from the console.
10.Restart your application server.
Tuning methodology
In the previous sections, you learned how to analyze and set the initial heap size. However, it
takes time to find an optimal value. Repeat the process of setting and analyzing the initial
heap size several times before you can get close to the optimal value. In an ideal situation,
you should plan for stress testing and tuning your applications before you deploy them on a
production server.
8.2.2 Web container
Each WebSphere Application Server contains a Web container that routes requests to a
transport queue between the Web server plug-in and the Web container. The Default Web
container properties are set for simple Web applications. However, these values might not be
appropriate for more complex Web applications. Therefore, you might have to adjust these
parameters to tune the Web container based on the specific needs of your environment.
122 WebSphere Application Server V6.0 for OS/400: A Guide to Getting Started
Thread pool
The thread pool settings within the Web Container is where you set the number of clients that
your application server can process concurrently. This greatly depends on your system’s CPU
speed, amount of memory, and number of disk arms.
We recommend that you set the value of the maximum size to handle the peak load on your
application server. Set it to a maximum size less that is than or equal to the number of threads
processing requests in your HTTP Server (powered by Apache). A value in the range of 25 to
50 is generally a good starting point for smaller Web applications. Use the Tivoli Performance
Viewer to monitor the number of threads being used to provide you with a better idea on the
value that you should set the maximum size value to.
To determine your current workload, use
Tivoli Performance Viewer to view real-time activity.
Access Tivoli Performance Viewer for your thread pool settings by using these steps:
1. Access the WebSphere Administrative Console.
2. Log in.
3. Expand Monitoring and Tuning Performance Viewer and click Current Activity (see
Figure 8-14).
Figure 8-14 Accessing
Chapter 8. Performance tips 123
4. In the next pane (Figure 8-15), select the name of the application server. In this example,
we select server1. Then click the Start Monitoring button to start the collection of data.
Figure 8-15 Tivoli Performance Viewer - Application Server
5. Click the server name link.
6. As shown in the pane in Figure 8-16, expand Performance Modules and select the
Thread Pools section.
Figure 8-16 Tivoli Performance Viewer - Thread Pools
7. Click the View Modules button. Real-time data is displayed in the lower right pane of your
window.

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