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Even though we are running tomcat 5, Apache Tomcat 6 by Wrox has been particularly helpful in tuning our tomcat 5.5.25 uportal JVM (just make sure you double check syntax...I ran into one instance it is slightly different). I'm sure their tomcat 5 book is good too but the thing that makes this book so good is that toward the back, it includes a good chapter on JVM tuning. I won't try to duplicat the chapter here by any means but I learned several things that I suspected but didn't know for sure. By default tomcat is set up in development mode. What this means is that by default it is set to do way more page compilation then necessary...in fact it is set to recompile each page every 4 seconds. Apache's suggested production settingsApache's suggested production settingsApache's suggested production settings say that setting the modicationTestInterval to a high value will improve performance a lot.
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