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8.3 Web server tuning tips
We applied several changes to the IBM HTTP Server (powered by Apache) configuration file.
The following sections identify the HTTP server parameters that affect performance and
explain how to change the values.
The ThreadsPerChild parameter defines how many concurrent threads can process clients
requests. It’s sometimes called the
Web server queue. Increasing this value allows the HTTP
server to process more clients requests. The other effect of increasing this value is that your
system or systems, where you run the HTTP server and WebSphere Application Server, must
be capable of supporting the increased workload.
For our test environment, we increased this value to 300 or higher. This value depends on the
size of your load.
Changing this parameter
To set these parameter, follow these steps:
1. Open your Web browser and access the following URL:
Here, your iSeries is the fully qualified host name of your iSeries system where you run the
2. Log in.
3. Click IBM HTTP Server for iSeries.
334 WebSphere Portal Express and Express Plus V5 for the IBM Eserver iSeries Server
4. Click the Advanced tab (see Figure 8-14).
Figure 8-14 Accessing the advanced settings for the HTTP server
5. On the next page (Figure 8-15), in the left navigation pane, under Global Settings, click
Global Server Settings.
Figure 8-15 Accessing global server settings
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6. In the Global Server Settings panel on the right, set the Number of threads: Maximum to a
desired value (see Figure 8-16). Click OK.
Figure 8-16 Changing the maximum number of concurrent threads
7. If you want to change this value on a per instance basis, select your HTTP server instance
in IBM Web Administration for iSeries.
8. In the navigation pane, under Server Properties, click General Server Configuration.
9. Select the General Settings tab.
Important: This change affects all HTTP servers that are created after this change is
336 WebSphere Portal Express and Express Plus V5 for the IBM Eserver iSeries Server
10.Change Number of threads to process requests to a desired value (see Figure 8-17). Click
Figure 8-17 Setting the maximum number of concurrent threads
11.Restart the server.
The connection time-out determines the number of seconds the server waits for a subsequent
request before it closes a persistent connection. Enabling persistent connections increases
the throughput of your server. Consider decreasing the connection time-out if you have simple
pages without images.
For our testing environment, we changed the KeepAliveTimeout setting to 5 (seconds). We
set this value to be less than the think time defined in our scripts because we want to be
conservative in our testing. Therefore, we assume each user will open new TCP connections
for each page view.
In a live environment, it can be helpful to increase KeepAliveTimeout. Keep in mind that a
higher KeepAliveTimeout value may increase contention for HTTP server processes. If you
are running out of HTTP processes, decrease this value.
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Changing this parameter
Perform these steps:
1. From the Server drop-down menu list (Figure 8-18), select your HTTP server instance.
Figure 8-18 Selecting the HTTP server
2. In the navigation pane, click System Resources.
3. Select the HTTP Connections tab.