Welcome to the user documentation for the Eclipse OpenJ9 virtual machine (VM).
This user documentation supports the configuration, tuning, and diagnosis of the OpenJ9 VM in an OpenJDK runtime. However, due to differences between the Java SE class libraries, specific options might apply only to one Java SE version. Icons are used to indicate where differences apply. For example:
This sentence applies only to Java 8 binaries that include the OpenJ9 VM. Icons for LTS releases are this colour.
This sentence applies only to Java 15 or later binaries that include the OpenJ9 VM. Icons for feature releases are this colour.
To see which Java releases are LTS releases and which are feature releases, and for information about release cadence, supported platforms, and build environments, see Supported environments.
Note: Documentation to support OpenJ9 is still under construction. The current content covers some high level information about OpenJ9 components together with the command-line options and environment variables that you can use to configure the VM when you start your application. Because OpenJ9 was contributed to the Eclipse Foundation by IBM, this content contains some links to additional information that forms part of the IBM® SDK, Java™ Technology Edition product documentation in IBM Knowledge Center. That content supplements the documentation here until a more complete set of user documentation is available.
We welcome contributions to the user documentation. If you would like to get involved, please read our Contribution guidelines. If you spot any errors in the documentation, please raise an issue at our GitHub repository.
OpenJDK binaries that contain the OpenJ9 VM are supported on a range of hardware and operating systems. This range is expanding as work progresses at the Eclipse foundation. See the current list of supported environments for details.
Note: This user guide also contains information about configuring, tuning, and debugging OpenJ9 on the z/OS® platform.
Documentation for specific releases
Several versions of the documentation are available, covering all releases of OpenJ9:
- Online documentation for the last release
- Online, in-progress documentation for the forthcoming release
- Downloads of earlier releases: to download a zip file, click the filename, then click Download. After downloading a
.zipfile, extract it, then open the
index.htmlfile in your browser.