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# Server --> Monitoring --> JRockit

Tasks Related Topics Attributes

## Overview

This tab is available only when you run a server with the JRockit Virtual Machine (VM). It 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.

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.

## Tasks

For information on specifying Java options, refer to Specifying Java Options for a WebLogic Server Instance.

## Related Topics

JRockit Java Virtual Machine documentation

## Attributes

Table 307-1

Attribute Label | Description | Value Constraints
--- | --- | ---
Used Heap | Indicates the amount (in bytes) of Java heap memory that is currently being used by the Virtual Machine. MBean: `weblogic.management. runtime. JRockitRuntimeMBean` Attribute: `UsedHeap` |
Used Physical Memory | Indicates the amount (in bytes) of physical memory that is currently being used on the host computer. This value reports the memory that is being used by all processes on the computer, not just by the Virtual Machine. MBean: `weblogic.management. runtime. JRockitRuntimeMBean` Attribute: `UsedPhysicalMemory` |
Total Nursery Size | Indicates 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: `weblogic.management. runtime. JRockitRuntimeMBean` Attribute: `TotalNurserySize` |
Max Heap Size | Indicates the maximum amount of memory (in bytes) that the Virtual Machine can allocate for its Java heap. This number is fixed at startup time of the VM, typically by the `-Mx` option. |
Gc Algorithm | Indicates 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: `weblogic.management. runtime. JRockitRuntimeMBean` Attribute: `GcAlgorithm` |
Total Garbage Collection Count | Indicates the number of garbage collection runs that have occurred since the Virtual Machine was started. MBean: `weblogic.management. runtime. JRockitRuntimeMBean` Attribute: `TotalGarbageCollectionCount` |
Last GcEnd | Indicates the time at which the last garbage collection run ended. MBean: `weblogic.management. runtime. JRockitRuntimeMBean` Attribute: `LastGcEnd` |
Last GcStart | Indicates the time at which the last garbage collection run started. MBean: `weblogic.management. runtime. JRockitRuntimeMBean` Attribute: `LastGcStart` |
Total GcTime | Indicates the number of milliseconds that the Virtual Machine has spent on all garbage collection runs since the VM was started. MBean: `weblogic.management. runtime. JRockitRuntimeMBean` Attribute: `TotalGcTime` |
GCHandles Compaction | Indicates whether the VM's garbage collector compacts the Java heap. Usually the heap is scattered throughtout available memory. A garbage collector that compacts the heap defragments the memory space in addition to deleting unused objects. MBean: `weblogic.management. runtime. JRockitRuntimeMBean` Attribute: `GCHandlesCompaction` | Valid values: true false
Concurrent | Indicates whether the VM's garbage collector runs in a separate Java thread concurrently with other Java threads. MBean: `weblogic.management. runtime. JRockitRuntimeMBean` Attribute: `Concurrent` | Valid values: true false
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: `weblogic.management. runtime. JRockitRuntimeMBean` Attribute: `Generational` | Valid values: true false
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: `weblogic.management. runtime. JRockitRuntimeMBean` Attribute: `Incremental` | Valid values: true false
Parallel | Indicates whether the VM's garbage collector is able to run in parallel on multiple processors if multiple processors are available. MBean: `weblogic.management. runtime. JRockitRuntimeMBean` Attribute: `Parallel` | Valid values: true false
Number Of Processors | Displays the number of processors on the Virtual Machine's host computer. If this is not a Symetric Multi Processor (SMP) system, the value will be `1`. MBean: `weblogic.management. runtime. JRockitRuntimeMBean` Attribute: `NumberOfProcessors` |
All Processors Average Load | Displays a snapshot of the average load of all processors in the host computer. If the computer has only one processor, this value is the same as JVM Processor Load. The value is returned as a double, where 1.0 represents 100% load (no idle time) and 0.0 represents 0% load (pure idle time). MBean: `weblogic.management. runtime. JRockitRuntimeMBean` Attribute: `AllProcessorsAvgLoad` |
JVM Processor Load | Displays a snapshot of the load that the Virutal Machine is placing on all processors in the host computer. If the host contains multiple processors, the value represents a snapshot of the average load. The value is returned as a double, where 1.0 represents 100% load (no idle time) and 0.0 represents 0% load (pure idle time). MBean: `weblogic.management. runtime. JRockitRuntimeMBean` Attribute: `JVMProcessorLoad` |
Total Number Of Threads | Indicates the number of Java threads (daemon and non-daemon) that are currently running in the Virtual Machine across all processors. MBean: `weblogic.management. runtime. JRockitRuntimeMBean` Attribute: `TotalNumberOfThreads` |
Number Of Daemon Threads | Indicates the number of daemon Java threads currently running in the Virtual Machine across all processors. MBean: `weblogic.management. runtime. JRockitRuntimeMBean` Attribute: `NumberOfDaemonThreads` |
Uptime | Indicates the number of milliseconds that the Virtual Machine has been running. MBean: `weblogic.management. runtime. JRockitRuntimeMBean` Attribute: `Uptime` |