What is the difference between Memory Usage and Heap Usage in my JVM Metrics ?
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From: Krist on 8 Feb 2010 18:08 Hi all, In my Apps Server console (OC4J) JVM Metrics, there are two columns about memory : Memory Usage (MB) -> Shows the amount of physical memory used by the JVM. Heap Usage (MB) -> Shows the amount of heap space used by the JVM. (heap usage seems to be up and down, but memory usage is never going down, even when all user already loggout.) What are the difference between the two ? Thank you for your help, xtanto
From: Krist on 8 Feb 2010 20:15
On 9 Feb, 08:09, Arne Vajhøj <a...(a)vajhoej.dk> wrote: > On 08-02-2010 18:08, Krist wrote: > > > In my Apps Server console (OC4J) JVM Metrics, there are two columns > > about memory : > > > Memory Usage (MB) -> Shows the amount of physical memory used by the > > JVM. > > Heap Usage (MB) -> Shows the amount of heap space used by the > > JVM. > > > (heap usage seems to be up and down, but memory usage is never going > > down, even when all user already loggout.) > > > What are the difference between the two ? > > I will guess that: > > memory usage = memory the JVM has allocated from the OS > > heap usage = memory your app has allocated from the JVM > > With two points: > > 1) the JVM need memory for internal stuff so memory usage > is greater than heap usage > 2) even if your app releases memory then the JVM may not > release it to the OS but keep it around just in case > you will need it again > > Arne Hi sirs, Thank you for your reply. So, is it only the heap area that I can tune ? (GC & Memory leak) How can I also tune the 'memory for internal stuff' usage ? Thank you, Krist |