NonStop Server for Java 5.1 Programmer's Reference
Heap Layout
In NonStop Server for Java 5.1, the memory is managed in generations (or memory pools) based on objects at
different ages for Java objects. Layout for generations is illustrated and described below.
Layout for Generations
The generations are:
Young (also called new) generation—The JVM allocates objects in the young generation pool. Minor
garbage collection happens when this young generation is full and the JVM is unable to allocate new
objects. The young generation also includes two survivor spaces. One survivor space is empty at any time
and serves as a destination of the next GC operation, which copies the collection of any live objects in Eden
and the other survivor space. Objects are copied between survivor spaces in this way until they are old
enough to be tenuredcopied to the tenured generation.
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Tenured (also called old) generation—The JVM moves objects that survived minor garbage collections from
the young generation to the old generation.
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Permanent generation—Class objects and metadata objects are allocated in permanent generation.●
The young and tenured generations each have an area called "Reserved," which is allocated at initialization and
used when garbage collection does not free sufficient space to satisfy the allocation request. In a Sun Microsystems
implementation, the address range for this area is reserved but memory space is not allocated until it is used.
Managing Generation Size
Several java command options allow you to manage the initial size and maximum size of the combined young
and tenured generations.
-Xms