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You also need to add the directive:
SetOutputFilter DEFLATE
to the container to be compressed, or globally if the compression can always be done. There is
documentation on the Apache website on mod_deflate
(http://httpd.apache.org/docs-2.0/mod/mod_deflate.html) that has information specific to setting up for
compression. That is the best place to look for details. The LoadModule and SetOutputFilter directives
are required for mod_deflate to work. Any other directives are used to further define how the
compression is done.
Since the compression support in Apache for i5/OS is a recent enhancement , Information Center
documentation for the HTTP compression support was not available when this paper was created. The
IBM HTTP Server or i5/OS website (http://www.ibm.com/servers/eserver/iseries/software/http/) will be
updated with a splash when the InfoCenter documentation has been completed. Until the documentation
is available, the information at http://httpd.apache.org/docs-2.0/mod/mod_deflate.html can be used as a
reference for tuning how mod_deflate compression is done.
Enabling Compression using IBM Webfacing Tool and WebSphere Application Server Support
You would configure compression using the Webfacing/WebSphere support in environments where the
internal HTTP server in WebSphere Application Server is used. This may be the case in a test
environment, or in environments running WebSphere Express V5.0 on an xSeries Server.
With the IBM WebFacing Tool V5.0, compression is ‘turned on’ by default. This should be ‘turned off’ if
compression is configured in Apache or if the LAN environment is a local high speed connection. This is
particularly important if the CPU utilization of interactive types of users (Priority 20 jobs) is about
70-80% of the interactive capacity. In order to ‘turn off’ compression, edit the web.xml file for a
deployed Web application. There is a filter definition and filter mapping definition that defines
compression should be used by the WebFacing application (see below). These statements should be
deleted in order to ‘turn off’ compression. In a future service pack of the WebFacing Tool, it is planned
that compression will be configurable from within WebSphere Development Studio Client.
<filter id="Filter_1051910189313">
<filter-name>CompressionFilter</filter-name>
<display-name>CompressionFilter</display-name>
<description>WebFacing Compression Filter</description>
<filter-class>com.ibm.etools.iseries.webfacing.runtime.filters.CompressionFilter</filter-class>
</filter>
<filter-mapping id="FilterMapping_1051910189315">
<filter-name>CompressionFilter</filter-name>
<url-pattern>/WFScreenBuilder</url-pattern>
</filter-mapping>
Additional Resources
The following are additional resources that include performance information for Webfacing including
how to setup pretouch support to improve JSP first-touch performance:
IBM i 6.1 Performance Capabilities Reference - January/April/October 2008
© Copyright IBM Corp. 2008 Chapter 6 - Web Server and WebSphere 115