<p>I know there is no "right" heap size, but which heap size do you use in your applications (application type, jdk, os)?</p>

<p>The JVM Options <code>-Xms</code> (initial/minimum) and <code>-Xmx</code> (maximum) allow for controlling the heap size. What settings make sense under which circumstances? When are the defaults appropriate?</p>

Typically i try not to use heaps which are larger than 1GB.
It will cost you on major garbage collections.
Sometime it is better to split your application to a few JVM on the same machine and not you large heap sizes.
Major collection with a large heap size can take >10 mintues (on unoptimized GC applications).