There are hundreds of JVM parameters or JVM Options exists inside sun JDK and its virtually impossible to keep track of every single JVM option and based on my experience we don't even use most of JVM flags except a couple of important JVM option related to java heap size, java options for printing garbage collection details and most likely JVM switches for setting up remote debugging in Java. but there are many other useful categories of JVM parameters that you at least like to be familiar with even if not intending to use them more frequently.