Class data sharing

CDS provides ability to share classes between Java virtual machines (JVMs). When classes are loaded by the JVM, they can be placed in a cache. When subsequent requests for that class are made, these requests are satisfied from the cache if possible rather than loading the class from a corresponding .jar file.

Refer:-
http://java.sun.com/j2se/1.5.0/docs/guide/vm/class-data-sharing.html