Weblogic 11g - Performance & Tuning using JConsole

Jconsole is a JMX-compliant monitoring tool.  It uses the extensive JMX instrumentation of the Java virtual machine to provide information on performance and resource consumption of applications running on the Java platform.

• Starting jconsole
• The jconsole interface
• Viewing summary information
• Monitoring Memory Consumption
• Monitoring Thread Use
• Monitoring Class Loading
• Monitoring and Managing MBeans
• Viewing VM Information
• Frequently Asked Questions

Starting jconsole

The jconsole executable is in JDK_HOME/bin, where JDK_HOME is the directory where the JDK is installed.  If this directory is on your system path, you can start the tool by simply typing jconsole in a command (shell) prompt. Otherwise, you have to type the full path to the executable file.

Command Syntax

You can use jconsole to monitor both local applications (those running on the same system as jconsole) and remote applications (those running on other systems). 

Note: Using jconsole to monitor a local application is useful for development and prototyping, but is not recommended for production environments, because jconsole itself consumes significant system resources. Remote monitoring is recommended to isolate the jconsole application from the platform being monitored.

For a complete reference on jconsole command syntax, see jconsole - Java Monitoring and Management Console.

Local Monitoring

To monitor a local application, it must be running with the same user ID as jconsole.  The command syntax to start jconsole for local monitoring is:

jconsole [processID]

where processID is the application's process ID (PID). To determine an application's PID:

• On Unix or Linux systems, use the ps command to find the PID of java.
• On Windows systems, use Task Manager to find the PID of java or javaw.

You can also use the jps command-line utility to determine PIDs.

For example, if you determined that the process ID of the Notepad application is 2956, then you would start jconsole as follows:

jconsole 2956

Both jconsole and the application must by executed by the same user name. The management and monitoring system uses the operating system's file permissions.

If  you don't specify a process ID, jconsole will automatically detect all local Java applications, and display a dialog box that lets you select the one you want to monitor (see the next section).

For more information, see Local JMX Monitoring and Management.

Remote Monitoring

To start jconsole for remote monitoring, use this command syntax:

jconsole [hostName:portNum]

where hostName is the name of the system running the application and portNum is the port number you specified when you enabled the JMX agent when you started the JVM. For more information, see Remote JMX Monitoring and Management.

If you do not specify a host name/port number combination, then jconsole will display a connection dialog box (see the next section) enabling you to enter a host name and port number.

Connecting to a JMX Agent

If you start jconsole with arguments specifying a JMX agent to which to connect, it will automatically start monitoring the specified JVM. You can connect to a different host at any time by choosing Connection | New Connection. and entering the necessary information.

Otherwise, if you do not provide any arguments when you start jconsole, the first thing you see is the connection dialog box.  This dialog box has three tabs:

• Local
• Remote
• Advanced

Local Tab

The local tab lists any JVMs running on the local system started with the same user ID as jconsole, along with their process ID and class/argument information.  Select the application you want to monitor, then click Connect.

Remote Tab

To monitor a remote JVM, enter:

• Host name: name of the machine on which the JVM is running.
• Port number: the JMX agent port number you specified when you started the JVM.
• User name and password: the user name and password to use (required only if monitoring a  JVM through a JMX agent that requires password authentication).

For information on setting the port number of the JMX agent, see Enabling the JMX Management Agent. For information on user names and passwords, see Using Password and Access Files.

To monitor the JVM running jconsole, simply click Connect, using host localhost and the port zero (0).

Advanced Tab

The advanced tab enables you to connect to other JMX agents (MBean servers) by specifying their JMX URL, and the user name and password.  The syntax of a JMX URL is described in the API documentation for javax.management.remote.JMXServiceURL.

Note: If the JMX agent is using in a connector which is not included in the Java platform, you need to add the connector classes to the classpath when running jconsole as follow:

jconsole -J-Djava.class.path=JAVA_HOME/lib/jconsole.jar:JAVA_HOME/lib/tools.jar:connector-path

where JAVA_HOME is the directory containing the JDK and connector-path is the directory or the jar file containing the classes not included in JDK 5.0 to be used by jconsole for connecting to a JMX agent.

The jconsole interface

The jconsole interface is composed of six tabs:

• Summary tab: displays summary information on the JVM and monitored values.
• Memory tab: displays information on memory use.
• Threads tab: displays information on thread use.
• Classes tab: displays information on class loading
• MBeans tab: displays information on MBeans
• VM tab: displays information on the JVM

The following sections provide information on each tab.

Viewing Summary Information

The Summary tab displays some key monitoring information on thread usage, memory consumption, and class loading, plus information on the JVM and operating system.

Summary

• Uptime: how long the JVM has been running
• Total compile time: the amount of time spent in just-in-time (JIT) compilation.
• Process CPU time: the total amount of CPU time consumed by the JVM

Threads

• Live threads: Current number of live daemon threads plus non-daemon threads
• Peak: Highest number of live threads since JVM started.
• Daemon threads: Current number of live daemon threads
• Total started: Total number of threads started since JVM started (including daemon, non-daemon, and terminated).

Memory

• Current heap size: Number of Kbytes currently occupied by the heap.
• Committed memory: Total amount of memory allocated for use by the heap.
• Maximum heap size: Maximum number of Kbytes occupied by the heap.
• Objects pending for finalization: Number of objects pending for finalization.
• Garbage collector information: Information on GC, including the garbage collector names, number of collections performed, and total time spent performing GC.

Classes

• Current classes loaded: Number of classes currently loaded into memory.
• Total classes loaded: Total number of classes loaded into memory since the JVM started, included those subsequently unloaded.
• Total classes unloaded: Number of classes unloaded from memory since the JVM started.

Operating System

• Total physical memory: Amount of random-access memory (RAM) that the OS has.
• Free physical memory: Amount of free RAM the OS has.
• Committed virtual memory: Amount of virtual memory guaranteed to be available to the running process.