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# Servers: Monitoring: JRockit

Configuration Options Related Topics

This page displays runtime data about the JRockit VM that is running the current WebLogic Server instance. It also displays information about the memory and processors on the computer that is hosting the VM.

The page is available only when you run a server with the JRockit Virtual Machine (VM).

To view additional data about the VM, such as how long it spends in a specific method, use the JRockit Management Console. You can also use the JRockit Management Console to send email notifications when specific VM events occur.

You cannot change the VM's operating parameters while the VM is active. Instead, use the startup options that are described in the JRockit documentation.

#### Configuration Options

Name | Description
--- | ---
Total Nursery Size | The amount (in bytes) of memory that is currently allocated to the nursery. The nursery is the area of the Java heap that the VM allocates to most objects. Instead of garbage collecting the entire heap, generational garbage collectors focus on the nursery. Because most objects die young, most of the time it is sufficient to garbage collect only the nursery and not the entire heap. If you are not using a generational garbage collector, the nursery size is ``0``. MBean Attribute: `JRockitRuntimeMBean.TotalNurserySize`
Max Heap Size | MBean Attribute: `JRockitRuntimeMBean.MaxHeapSize`
Gc Algorithm | The type of garbage collector (GC) that the Virtual Machine is using. JRockit provides the following types of GCs: Generational Copying, which is suitable for testing applications on a desktop machine with a small (less then 128 MB) heap. Single Spaced Concurrent, which reduces or eliminates pauses in the VM that are due to garbage collection. Because it trades memory throughput for reduced pause time, you generally need a larger heap size than with other GC types. If your ordinary Java threads create more garbage than this GC can collect, the VM will pause while the Java threads wait for the garbage collection to finish. Generational Concurrent, which creates a "nursery" space within the heap. New objects are created within the nursery. When the nursery is full, JRockit "stops-the-world," removes the dead objects from the nursery, and moves live objects to a different space within the heap. Another thread runs in the background to remove dead objects from the non-nursery space. This GC type has a higher memory throughput than a single spaced concurrent GC. Parallel, which allocates all objects to a single spaced heap. When the heap is full, all Java threads are stopped and every CPU is used to perform a complete garbage collection of the entire heap. This behavior causes longer pause times than for the concurrent collectors but maximizes memory throughput. MBean Attribute: `JRockitRuntimeMBean.GcAlgorithm`
Total Garbage Collection Count | The number of garbage collection runs that have occurred since the Virtual Machine was started. MBean Attribute: `JRockitRuntimeMBean.TotalGarbageCollectionCount`
GCHandles Compaction | Indicates whether the VM's garbage collector compacts the Java heap. Usually the heap is scattered throughout available memory. A garbage collector that compacts the heap defragments the memory space in addition to deleting unused objects. MBean Attribute: `JRockitRuntimeMBean.GCHandlesCompaction`
Concurrent | Indicates whether the VM's garbage collector runs in a separate Java thread concurrently with other Java threads. MBean Attribute: `JRockitRuntimeMBean.Concurrent`
Generational | Indicates whether the VM's garbage collector uses a nursery space. A nursery is the area of the Java heap that the VM allocates to most objects. Instead of garbage collecting the entire heap, generational garbage collectors focus on the nursery. Because most objects die young, most of the time it is sufficient to garbage collect only the nursery and not the entire heap. MBean Attribute: `JRockitRuntimeMBean.Generational`
Incremental | Indicates whether the VM's garbage collector collects (increments) garbage as it scans the memory space and dumps the garbage at the end of its cycle. With a non-incremental garbage collector, garbage is dumped as soon as it is encountered. MBean Attribute: `JRockitRuntimeMBean.Incremental`
Parallel | Indicates whether the VM's garbage collector is able to run in parallel on multiple processors if multiple processors are available. MBean Attribute: `JRockitRuntimeMBean.Parallel`
Number Of Processors | The number of processors on the Virtual Machine's host computer. If this is not a Symmetric Multi Processor (SMP) system, the value will be `1`. MBean Attribute: `JRockitRuntimeMBean.NumberOfProcessors`
Total Number Of Threads | The number of Java threads (daemon and non-daemon) that are currently running in the Virtual Machine across all processors. MBean Attribute: `JRockitRuntimeMBean.TotalNumberOfThreads`
Number Of Daemon Threads | The number of daemon Java threads currently running in the Virtual Machine across all processors. MBean Attribute: `JRockitRuntimeMBean.NumberOfDaemonThreads`

Related Topics

- JRockit Documentation