The Upgrade Tool migrates the configuration, deployed applications, and certificate databases from an earlier version of the Application Server to the current version. The Upgrade Tool does not upgrade the binaries of the Application Server. The installer is responsible for upgrading the binaries. Database migrations or conversions are also beyond the scope of this upgrade process.
Only those instances that do not use Sun GlassFish Web Server-specific features are upgraded seamlessly. Configuration files related to HTTP path, CGI bin, SHTML, and NSAPI plug-ins are not be upgraded.
Before starting the upgrade process, make sure that you stop all server instances, node agents, and domains (in that order) in the source server (the server from which you are upgrading) and the target server (the server to which you are upgrading).
Application archives (EAR files) and component archives (JAR, WAR, and RAR files) that are deployed in the Application Server 8.x environment do not require any modification to run on Enterprise Server.
Applications and components that are deployed in the source server are deployed on the target server during the upgrade. Applications that do not deploy successfully on the target server must deployed manually on the target server by the user1
If a domain contains information about a deployed application and the installed application components do not agree with the configuration information, the configuration is migrated as is without any attempt to reconfigure the incorrect configurations.
In Application Server 8.x, the clusters are defined in the domain.xml file and there is no need to specify clusters separately. Another notable difference is that in Application Server 8.x, all the instances within a cluster reside within the same domain and therefore, in the same domain.xml file.
The Upgrade tool transfers certificates from the source certificate database to the target. The tool transfers security policies, password files from standard, file-based realms, and custom realm classes.
After you have upgrade a domain, you can see a file whose name is in the following format: upgradedTo<releasenumber>. For example, a domain that has been upgraded to 9.1 Update 1 will have a file called upgradeTo91 in its config folder.
You can cancel the upgrade process only if you are running the Upgrade Tool in GUI mode.