Sun Java System Web Server 6.1 SP9 Performance Tuning, Sizing, and Scaling Guide

Cache Not Utilized

If the cache is not utilized, your server is not performing optimally. Since most sites have lots of GIF or JPEG files that should always be cacheable, you need to use your cache effectively.

Some sites, however, do almost everything through CGIs, SHTML, or other dynamic sources. Dynamic content is generally not cacheable, and inherently yields a low cache hit rate. Do not be too alarmed if your site has a low cache hit rate. The most important thing is that your response time is low. You can have a very low cache hit rate and still have very good response time. As long as your response time is good, you may not care that the cache hit rate is low.

Check your hit ratio using statistics from perfdump or the Monitor Current Activity page of the Server Manager. The hit ratio is the percentage of times the cache was used with all hits to your server. A good cache hit rate is anything above 50%. Some sites may even achieve 98% or higher. For more information, seeCache Information

In addition, if you are doing a lot of CGI or NSAPI calls, you may have a low cache hit rate. If you have custom NSAPI functions, you may also have a low cache hit rate.