Garbage Collector periodic rate

Question

Hello!
In an application which I'm studying, garbage collector (opportunely configured with command line options) run on a configurable periodic time: this means that every (10 minutes for example) I call method System.gc() in my code.
If I don't explicitily call this method, Java virtual machine will intervene by itself?
Will it intervene only when a threshold amonut of memory is consumed (too many JAVA object instantiated which wait for be freed) ?
Thank you very much in advance
Diego

Answer 1

Does anyone knows what's the difference with Full GC
and why it intervenes ? Because you told it to. You called System.gc().
I don't think that was the question you meant. My guess is you wanted to know why the Concurrent Low Pause Garbage Collector intervened?
Off that first link I gave you was an link to an article that describes the GC output log ( http://java.sun.com/docs/hotspot/gc1.4.2/example.html ). If you read that article it describes what each of the values in the gc output means.
From that article:
[GC [<collector>: <starting occupancy1> -> <ending occupancy1>, <pause time1> secs] <starting occupancy3> -> <ending occupancy3>, <pause time3> secs]
where
<collector> is an internal name for the collector used in the minor collection
<starting occupancy1> is the occupancy of the young generation before the collection
<ending occupancy1> is the occupancy of the young generation after the collection
<pause time1> is the pause time in seconds for the minor collection.
<starting occupancy3> is the occupancy of the entire heap before the collection
<ending occupancy3> is the occupancy of the entire heap after the collection
<pause time3> is the pause time for the entire garbage collection. This would include the time for a major collection is one was done.
The reason the Concurrent Mark Sweep(CMS) starts is also in the first link I gave you. When the Concurrent Garbage Collector thinks you are about to run out of heap it starts the CMS.
1234.306: [GC [1 CMS-initial-mark: 342810K(499712K)] 342906K(524224K), 0.0026879 secs]In your case that was when the used heap reached 342810K out of a current allocated heap of 499712K
You could describe the specific problem you are investigating. Also it would be helpful if you provided the VM parameters you have for starting your application.