Diagnostics Guide

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About the Oracle JRockit JDK

Note: The information in the Diagnostics Guide is only applicable to the Oracle JRockit JDK R26 and later versions.

The Oracle JRockit JDK provides tools, utilities, and a complete runtime environment for developing and running applications using the Java programming language. The JRockit JDK includes the Oracle JRockit Java Virtual Machine (JVM). The Oracle JRockit JVM is developed and optimized for Intel architectures to ensure reliability, scalability, and manageability for Java applications.

This section contains information on the following subjects:


What is the JRockit JVM?

The JRockit JVM is a high performance JVM developed to ensure reliability, scalability, manageability, and flexibility for Java applications. The JRockit JVM delivers a new level of performance for Java applications deployed on Intel 32-bit (Xeon) and 64-bit (Xeon, Itanium, and SPARC) architectures at significantly lower costs to the enterprise. Furthermore, it is the only enterprise-class JVM optimized for Intel architectures, providing seamless inter operability across multiple hardware and operating configurations. The JRockit JVM makes it possible to gain optimal performance for your Java applications when running it on either the Windows or Linux operating platforms on either 32-bit or 64-bit architectures. The JRockit JVM is especially well suited for running Oracle WebLogic Server.

For more information on JVMs in general, see the Introduction to the JVM Specification at:


About the JDK

The JRockit JVM is one component of the Oracle JRockit Java development kit (JDK). In addition to the JRockit JVM, the JDK is comprised of the Java Runtime Environment (JRE), which contains the JVM and Java class libraries (as specified by the Java Platform, Standard Edition 6 API Specification), as well as a set of development tools, such as a compiler. For more information about the contents of the JRockit JDK, please refer to The Contents of a JRockit JDK Installation.


JRockit JDK Versions

The JRockit JDK numbering scheme is based upon:

For example, Oracle JRockit JDK 6 R27.6 refers to the 27.6 release of JRockit JVM used with Java SE 6; Oracle JRockit JDK 1.4.2 R27.6 refers to the 27.6 release of the JRockit JVM used with J2SE 1.4.2. All future versions of the JRockit JDK will follow this versioning scheme.

A full version name might look like this:


where R27.6.0 is the JRockit JVM release, 1.6.0_01 is the Java version, and windows-ia32 is the platform on which this version runs.

Note: JRockit JDK versions that were based on J2SE releases earlier than 1.4.2 used a different numbering scheme following the Oracle WebLogic Platform versions. For this reason, the J2SE 1.3.1 version of the JRockit JDK was called 7.0.

Every JRockit JVM release comes with several Java versions. For example, JRockit JVM R27.6 comes with Java SE versions 1.4.2, 5.0, and 6. A Java version can be compatible with multiple JRockit JVM releases.


What Platforms Does the JRockit JDK Support?

The JRockit JDK is certified to be compatible with J2SE 1.3.1, 1.4.2, 5.0, and Java SE 6. For a complete list of platforms that the JRockit JDK supports, please refer to JRockit JDK Supported Configurations at:



Compatibility Information

The JRockit JDK subscribes to an update policy that ensures compatibility from one release to the next to provide simple and complete upgrade flexibility. This policy is described in Compatibility Between Releases at:



The Contents of a JRockit JDK Installation

This section describes the various components that make up an installation of the JRockit JDK. It also identifies the folders in which the components reside.

The JRockit JDK is very similar, in the file layout, to the Sun JDK, except that it includes a new JRE with the JRockit JVM and some changes to the Java class libraries (however, all of the class libraries have the same behavior in the JRockit JDK as in the Sun JDK).

The following sections briefly describe the contents of the directories in a JRockit JDK installation:

Development Tools

Found in: /bin

Development tools and utilities help you develop, execute, debug, and document programs written in the Java programming language. The JRockit JDK includes the standard tools commonly distributed with the typical Java JDKs. While most of these are standard JDK tools and are proven to work well with Java development projects, you are free to use any other third party tools, compilers, debuggers, IDEs, and so on that might work best in your situation. The tools included with the JRockit JDK are:

For more information on these tools, please refer to Sun Microsystem’s Java SE 6 Development Kit at:



Found in: /demo

This directory contains various demos of how to use various libraries included in the JRockit JDK installation.

C Header Files

Found in: /include

Header files that support native-code programming using the Java Native Interface (JNI) and the Java Virtual Machine Tools Interface (JVMTI) and other functionality of the Java SE Platform.

Java Runtime Environment (JRE)

Found in: /jre

The JRockit JVM implementation of the Java runtime environment. The runtime environment includes the JRockit JVM, class libraries, and other files that support the execution of programs written in Java.

Java Virtual Machine

By definition, the JVM is the JRockit JVM, as described in this documentation set.

Standard Java SE JRE Features

In addition to JRE components specific to the JRockit JDK, the JRE also contains components found in the Sun implementation of the JRE. For a complete list of the standard Java SE JRE features, see the Sun documentation for the specific version of JRockit JDK you are running:

Note on JRE Class Files

The JRE class files distributed with the JRockit JDK come directly from Sun, except for a small number that are tightly coupled to the JVM and are therefore overridden in the JRockit JDK. The overridden class files are in the java.lang, java.io, java.net, and java.util packages. No classes have been omitted.

Additional Libraries

Found in: /lib

Additional class libraries and support files required by the development tools.


Found in: /sample

The Sample directory contains the source files for a simple NIO-based HTTP/HTTPS Server written in Java. The server was written to demonstrate some of the functionality of the Java 2 platform. The demo is not meant to be a full tutorial, it assumes that you have some familiarity with the subject matter.


Attach API Support

Versions of the JRockit JVM running on Java 6 support the Attach API. This API is a Java extension that provides a way to attach tools written in Java to JRockit JVM and load their tool agents into it. For example, a management console might use a management agent to obtain objects in the JRockit JVM instance. If the management console has to manage an application running in a JRockit JVM instance that doesn’t include the management agent, you can use this API to attach to the JRockit JVM instance and load the agent.

For more information, please see the Attach API specification at:



Oracle JRockit Documentation

The Oracle JRockit JVM Diagnostics Guide is a general document applicable to the R27 release and all subsequent JRockit JDK releases.

For links to all documentation available for the latest version of the JRockit JDK, visit the Oracle JRockit documentation page at the following location:


From this page, you can also access the documentation for earlier versions of the Oracle JRockit JDK.

You can find documentation for the Oracle JRockit Mission Control tools at the following location:



JRockit JVM Command Line Options

The Oracle JRockit JVM configuration and tuning parameters are set by using specific command line options, which you can enter either along with the start-up command or include in a start-up script. These options are discussed in the Oracle JRockit Command Line Reference, at:



JRockit JDK and JRockit Mission Control Support

You are entitled to support on the JVM and JRockit Mission Control if you have a support agreement with Oracle.

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