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Basic Facts about Zulu® Enterprise

What is Azul Zulu Enterprise?

Zulu Enterprise builds of OpenJDK are 100% open source Java Development Kits (JDKs) that are compliant with the Java SE standard. Zulu Enterprise subscriptions provide timely security updates, bug fixes, and Premium and Standard support options for businesses whose operations depend upon Java. Zulu Enterprise can be deployed across various operating systems, containers, hypervisors and cloud platforms. Zulu Enterprise binaries are built from the OpenJDK project sources and include backports of bug fixes and security updates after the relevant OpenJDK project no longer publishes such updates. 

What is a “certified” build of OpenJDK?

Zulu is verified compliant with the Java Standard Edition (“Java SE”) specifications using the OpenJDK Community Technology Compatibility Kit (TCK) licensed from Oracle. The TCK is a suite of more than 120,000 tests which ensures that a binary build of OpenJDK meets all the specifications of the individual JSRs for a given version of Java SE (e.g. Java 8). Azul is one of a small number of organizations and companies that licenses the TCKs for Java SE.  In addition to running the TCKs on all Zulu builds, the Zulu QA team also performs extensive testing against a wide range of application stacks and open source projects.

How are Zulu Enterprise subscriptions priced?

Zulu Enterprise is priced on a subscription basis based upon the number of supported systems (desktops and/or virtual or physical servers) running Java applications. Here’s our pricing:

Max # of Supported Systems Price/Year (Standard Support) Price/Year (Premium Support)
25$13,200Not available

Your Azul Sales representative will provide pricing that matches your specific requirements and help you maximize the value of your Zulu® Enterprise Subscription.

How is Zulu Enterprise licensed?

 Zulu is licensed identically to OpenJDK, which is under GPLv2 with Classpath Exception, in addition to other third-party licenses.

What Zulu OpenJDK packages and Java versions are available?

Today, Zulu supports Java SE 11, 10, 9, 8, 7, and 6. Azul provides free community builds of Zulu on our download page and JDKs plus JRE bundles to Zulu Enterprise subscribers. Zulu is certified on the following operating systems:

Operating SystemJDK 11JDK 10JDK 9JDK 8JDK 7JDK 6

Windows: Client: 10, 10 IoT Core, 8.1, 8, 7;                   Server: 2016, 2012R2, 2012, 2008R2

Linux: RHEL, CentOS, Ubuntu, Debian, SLES, Oracle Linux, Amazon Linux, Container Linux, Alpine Linux
macOS: Sierra, High Sierra 
Solaris: V10, V11

Further detail on Zulu supported platforms can be found at https://www.azul.com/products/zulu-enterprise/supported-platforms/. Exact platforms and major versions are listed in product release notes as new versions and target types get added regularly.

Does Zulu Enterprise support desktops?

Absolutely! See the table above for some examples of the various client operating systems that Zulu Enterprise supports, including Windows and macOS.

What are Zulu Community Builds?

Azul makes certain versions of the full Zulu JDK freely accessible from the Zulu download site. These “Zulu community” builds are builds of OpenJDK versions which are (currently or soon to be) available in the relevant OpenJDK project. Subscribers to Zulu Enterprise have access to builds that will continue to be updated even after the relevant OpenJDK project no longer publishes such updates and will include backports of bug fixes and security updates. 

What does Zulu Enterprise support consist of?

Azul offers a variety of support capabilities for certified Zulu Enterprise binary distributions, including security updates and backported bug fixes as well as 24x7x365 live support. Zulu Enterprise builds will continue to be updated even after the relevant OpenJDK project no longer publishes such updates and will include backports of bug fixes and security updates during the supported lifecycle. The Zulu product is supported by a dedicated team of engineers and QA professionals that provide tier 1, 2 & 3 support, including root cause analysis and temporary patches in addition to backporting bug fixes and security patches. Support is available both for current releases and older versions (e.g. Java 7 and 6). You can view all of Azul’s support terms at https://www.azul.com/products/azul_support_roadmap/.

Are there performance differences between Zulu Enterprise and Oracle HotSpot?

The quick answer is no. Any variation between benchmarking Zulu (OpenJDK) vs. HotSpot is typically the same as variations found comparing multiple runs using the same JVM.

Does Azul offer mission-critical support for Zulu Enterprise?

Azul has a proven track record in supporting mission-critical applications 24x7x365 for the world’s largest companies globally. You can view selected Azul customer logos on our Customer Success page. Our support team is geographically and globally dispersed and are experts in Java deployments and triaging JVM/JDK-related issues.

What is your product release velocity across your different Zulu Enterprise support offerings?

Zulu follows OpenJDK’s quarterly scheduled updates (i.e. OpenJDK critical patch updates or “CPUs”) and responds to any midcycle critical security updates released by Oracle or other contributors to OpenJDK such as Azul and Red Hat. Azul reviews the Common Vulnerabilities and Exposures (“CVE”) list for a given security update to identify which code modules have been modified, whether those are relevant for Zulu, and, with our release notices, provide a summary of change impact. Azul also backports bug fixes and security updates made to newer versions of Java (e.g. Java 11) to older versions of Java (i.e. Java 8, 7 and 6). Due to the sensitive nature of security details, Azul only publishes the CVE details in the Zulu Enterprise release notes and provides these directly to subscribers. Zulu public user documentation does not enumerate any CVE details.

Does Azul upstream bug fixes?

Yes, Azul’s OpenJDK committers upstream all changes and bug fixes back to the OpenJDK community. 

How does Zulu accommodate Oracle and OpenJDK moving to LTS and 6-month feature releases starting with Java 9?

Starting with Java 9, Azul announced that each Java SE feature release will have a medium-term support, or long-term support designation (i.e. “MTS”, or “LTS”, respectively). LTS releases occur every three years. MTS feature releases occur annually in the off-years in between LTS releases. Releases designated as LTS have a 10-year support lifecycle, and those designated as MTS have support lifecycles that extend beyond the introduction of the next LTS release. Zulu’s MTS releases allow for the use of new features created in OpenJDK and with formal support. The goal is giving early adopters trusted support on feature releases without waiting upwards of three years for the next LTS cycle to begin.

Technical Facts and Compatibility with Oracle HotSpot

Is Zulu supported in Cloud, virtualized, or containerized environments?

Yes to all three. Azul has strategic partnerships with major ISVs and cloud providers and will support Zulu on all cloud, virtualization, or containerized platforms where any supported client OS runs.

Can I use Zulu with Eclipse?

Yes, Zulu is a fully Java SE compliant JVM and can be used with any IDE or any other development tool that supports Java SE.  

Is there any additional functionality available with Zulu?

In addition to the standard JDK, Azul ships the open source FreeType font rendering library with each Zulu JDK. Azul also makes available add-on packages, including Zulu Commercial Compatibility Kit (CCK) and the Zulu Cryptography Extension Kit, which contains extended cipher lengths policy files. The CCK contains additional functionality that is not included in the OpenJDK source, but which will help ensure compatibility in applications that utilize certain features that Oracle bundles with HotSpot outside the specifications of Java SE. The Zulu CCK is free and can be added easily to Zulu as part of your normal software update process. Currently, the CCK contains Monotype™ fonts.

Is OpenJDK similar to Oracle HotSpot?

OpenJDK is the reference implementation for Java SE. HotSpot is the brand name that Oracle may use for its commercial JDKs and JREs. All development by Oracle and others in the Java Community (Red Hat, IBM, Azul, and others) for Java 7 and later versions was and is done completely in the open as part of the OpenJDK project. The only exception to this open development process is related to security fixes, where development is done in private and source changes are only introduced into the OpenJDK source base on specific scheduled (typically quarterly) timeframes. Oracle does add some closed source components within their HotSpot-based products, including font libraries, some of which are available from Azul in the Zulu Commercial Compatibility Kit (CCK). The fact that OpenJDK and Oracle HotSpot are created from the same underlying source code is exactly why OpenJDK builds and Oracle HotSpot are largely indistinguishable except for some areas that are outside the specifications of Java SE and are further described below.

What are the technical differences between OpenJDK and Oracle HotSpot?

Many closed source components that Oracle ships with Oracle JDK are compatible with OpenJDK, but are not part of the Zulu (or any other OpenJDK) distributions. These include Mission Control, Flight Recorder, Visual VM, Derby DB, Java Web Start, Applets/JRE Browser plug-in, JavaFX, Font Rendering/Fonts, Cryptography Extensions, SNMP Protocol Adapter, Color Matching, Anti-Aliased 2D Rendering, and the JavaScript engine (pre 8.x). Select details are listed below.

Does Zulu have any font rendering/font differences compared to Oracle HotSpot?

Possibly. Oracle HotSpot utilizes T2K, a third party closed source font rendering library, in addition to Monotype Lucida font files. OpenJDK depends on the FreeType font rendering library which Zulu also integrates. There are certain rare situations where the rendering between T2K and FreeType can be slightly different. As OpenJDK does not include Lucida fonts, Azul also makes available relicensed copies of the Lucida fonts via the Zulu Commercial Compatibility Kit (CCK).

Does Zulu use Cryptography Extensions?

The Zulu Cryptography Extension Kit (CEK) package provides the same unlimited cipher strength as Oracle’s JCE add-on. It ships as an add-on to Zulu.

Does Zulu use JavaFX?

Java FX is an Oracle product that was released to the OpenJDK project in 2017. OpenJFX is not part of OpenJDK JDK/JRE distributions and is therefore not included in Zulu distributions. Azul does provide commercial support for OpenJFX, and those interested in OpenJFX support should contact their Azul sales representative.

Does Zulu support the Java Mission Control or Flight Recorder commercial features?

Not at this time. Oracle open sourced both Mission Control and Flight Recorder in 2018. Azul is assessing providing commercial support for the open source versions of Mission Control and Flight Recorder. Contact your Azul sales representative to learn more.

Does Zulu include the SNMP Protocol Adapter?

No. The SNMP protocol adapter is not part of the Java SE standard or the OpenJDK project, but Oracle does integrate it as part of HotSpot. It is recommended that Zulu customers use JMX instead, which is part of the Java SE standard.

Which Color Matching library does Zulu use?

Oracle JDK ships the third party KCMS color matching library from Kodak. OpenJDK and Zulu use the LCMS open source color matching library.

Which Anti-Aliasing 2D rendering library does Zulu use?

Oracle JDK 9, OpenJDK 9, and Zulu 8 and 9 include the Marlin open source library. Older Oracle releases (Oracle JDK 8 and prior) ship the third-party Ductus anti-aliasing library. Older OpenJDK releases (JDK 8 and prior) and older Zulu releases (JDK 7 and prior) use the Pisces open source rendering library.

Which JavaScript engine does Zulu use?

Oracle JDK, OpenJDK, and Zulu for JSE 8 all ship the same Nashorn engine for running JavaScript. Oracle JDK 7 and 6 ship the Mozilla Rhino engine. Azul provides the Mozilla Rhino engine as an add-on to Zulu 7. OpenJDK and Zulu 6.x are compatible with Rhino, but neither provides the Rhino engine as part of the distribution.

Are there any technical differences between Zulu community downloads and the Zulu Enterprise binaries shipped to customers?

Zulu community downloads are always full JDKs, targeting developer-focused use cases and represent the top-of-tree OpenJDK. Zulu Enterprise subscribers have access to JDK and JRE builds, and other tailored builds, targeting both developer and production use cases. Out-of-cycle bug fixes and security updates also appear in builds of Zulu Enterprise prior to their eventually being contributed to OpenJDK.

Useful Basic Definitions:

OpenJDK is the open source project where all new Java versions (Java 7 and beyond) are created and older versions maintained.

Java SE is the standard (specification, reference implementation, and test suite) that an implementation must pass to be certified as Java compliant.

Zulu is Azul’s binary distribution of OpenJDK that adheres to the Java SE standard and is a compliant implementation.


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