To properly configure the java heap one must understand how it is structured. The heap is divided into two areas, New and Old . The new category is sub-divided further into three areas, Eden , To and From . Eden is the area where new objects are place when they are created. When a garbage collection occurs, live objects within Eden are promoted and placed in To .
Objects move between To and From until they exceed a maximum threshold.
When this occurs, they are moved out of the New arena and into the Old . HotSpot is designed to quickly clean up objects within the New arena. GC within the New arena are referred to as scavenges and occur quickly. The algorithm for GC within the Old arena is more complicated and costly. When objects within the Old arena need to be collected, the GC performs a mark-compact algorithm.