208 Maximum Performance with WebSphere Application Server V5.1 on iSeries
Triggered Cache Manager (TCM) is a component in the iSeries server that was created
exactly for this purpose. This component is packaged in the IBM HTTP Server for iSeries,
5722-DG1 Option 1. TCM is a Transmission Control Protocol (TCP) server. This server may
be used in conjunction with Web servers and Web document caching agents to keep Web
sites running at peak performance.
TCM is:
A cache manager, not a cache or cache server
Based on trigger messages
This means that you must set up application triggers for the server to work. These
messages are sent to the TCM via the HTTP protocol.
A stand-alone server that can work with multiple types of caching mechanisms, for
example caching routers, proxy caches, and so on
It is useful in the environment that we describe here for the HTTP Server (powered by
Apache), but it can be used for the HTTP Server (original), Lotus® Domino®, or
WebSphere Application Server environments as well.
TCM is proactive (based upon updates to an LOB database) in the update of Web content.
TCM causes the Web content to be dynamically regenerated and then placed in a location
(usually the iSeries IFS) that was configured to be served as static content by your Web
server. The TCM is most effective for a Web site that has a large number of requests for
content that is somewhat constant, but changes frequently.
One of IBM’s first uses of the TCM concept was to drive the 1996 Summer Olympic Games
Web site. For example, a downhill skiing results page (mostly HTML) was composed of
hundreds of dynamic items including names, times, scores, and so on for a particular event.
For every request of that page, consider if the application server had to re-run all the
database queries to dynamically calculate the content. That level of activity could have
weighed heavily on the server with many repetitive actions. Only when the application LOB
data was updated with new results, then the application server was used to update a standard
results page to be served from a “static” portion of your Web site. This tremendously reduced
the burden on the application server.
For more information, read HTTP Server (powered by Apache): An Integrated Solution for
IBM Eserver iSeries Servers, SG24-6716.
6.5.3 mod_deflate
mod_deflate is a tool used to compress files server from the HTTP Server. This is done
through the configuration files and is the equivalent of Apache’s mod_gzip. When Web
content or files are compressed, it reduces the amount of bandwidth required to send the
information. The data is eventually decompressed on the client side in the Web browser. Keep
in mind that additional resources are consumed to compress and decompress the content.
Unless you expect or suspect bandwidth issues, mod_deflate is not necessary.
6.5.4 Logging
There are several different areas of logging to consider for the HTTP Server. And depending
on your needs or performance problem, you may or may not want them collecting detailed
information. Remember, the more you collect, the more resources are used to write to disk.
Chapter 6. Tuning the IBM HTTP Server (powered by Apache) 209
Access logs
One of the most important tuning options when it comes to logging has to do with the Access
Log. By default, this log is turned on, and all HTTP requests are captured.
To turn off the HTTP server Access Log, follow these steps:
1. Access your HTTP server configuration page in IBM Web Administration for iSeries.
2. Under Tools, click Edit Configuration File.
3. Search for a line with the text CustomLog (see Figure 6-4). Comment out this line by placing
the pound symbol (#) in front of the line.
Figure 6-4 Disabling the access log
4. Save and close the configuration file.
5. Restart the IBM HTTP Server.
The default value for the access logs is
enabled for an incoming HTTP request. The
recommended value for performance reasons is to disable the access logs.
Error logs
The error log for the HTTP Server can be setup at several different levels. Depending on that
level, your performance can degrade. The bottom line is that the more you log, the more
resources are consumed and the performance of your application decreases. Different levels
of logging are:

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