5.2 The User Region
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## 5.2 The User Region

The user region isolates the kernel from deployed applications, including both your own user applications and the user-oriented VTS applications such as the Admin Console. This means that the kernel is mostly invisible to applications and to application management. This is because most of the kernel bundles are not installed in the user region (apart from a few needed for region management). The necessary function to support the kernel runs in the OSGi framework, but the user region applications cannot see it, except for the services that are normally offered.

This way of implementing VTS greatly simplifies the administration tasks you perform. In particular, when you use the Admin Console to manage Web Server, you do not see the many bundles that are internal to the kernel. The only exceptions are bundles in the kernel region, typically just the system bundle, which are configured to be visible in the user region and the kernel bundles that VTS uses for region management, which are required to be installed in the user region.

This isolation has many other benefits. For example, it is not necessary for the kernel and user applications to use the same version of the Spring Framework. In fact the kernel installs only those parts of the Spring Framework that it needs. If you update the kernel, it is far less likely that you will also need to upgrade or adjust the applications to accomodate a new version of the kernel. The kernel implementation is therefore much more stable and resilient and applications are much more likely to survive kernel upgrades between releases.

When you install VTS, the kernel creates a single user region. The kernel and the user region are configured independently of each other; see Configuring VTS for details.

Finally, the isolation provided by the user region together with scoped applications and plans solve common dependency problems that occur when using OSGi.

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