You might want to do this if the heap for a JVM has hit its maximum allowablesize, but there is additional physical memory on the machine that another JVM could use.
如果一个JVM堆已达到其允许最大值，但机器上还有更多物理内存、另一个JVM可以使用，你可以这样做。
3
YES setting everything max allowablesize opens the door for potential denial-of-service attacks - that's the reason it's NOT set to 2 GB for each of those size values in the first place!