# Upgrade Tool: An Overview

Use the Upgrade Tool to transfer configuration information to a Sun GlassFish Enterprise Server 2.1 installation.

Information that is transferred includes data about deployed applications, the file realm, security certificates, and other resource and server configuration settings.

## Upgrade Terminology

The following are important terms related to the upgrade process:

- Source Server: the installation from which you are upgrading to the new version.

- Target Server: the installation to which you are upgrading.

- Domains Root : the directory where the domains are created. This directory, by default, is the location specified as `AS_DEF_DOMAINS_PATH` in `asenv.conf`

- Domain Directory or domain-dir: The directory (within the Domains Root) corresponding to a specific domain. All the configuration and other data pertaining to the domain exists in this directory.

- Install Root: the directory where the Application Server is installed.

If the Upgrade checkbox was selected during the Application Server installation process, the Upgrade Wizard screen will automatically display after the installation completes. The upgrade process starts.

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