Before you begin the process of migrating to WebSphere Application Server Version 6.1, there are some considerations of which you need to be aware.
Prior levels of WebSphere Application Server will continue to run at the higher prerequisite levels.
In particular, note that the default daemon port definition for both versions is the same when installing to coexist with WebSphere Application Server Version 5.x or 6.0.x.
See Port number settings in WebSphere Application Server versions for default port information.
See Coexisting.
If you installed an application in your old environment with Use Metadata From Binaries set to true and during that installation or a future update of the application you made a change to the application's metadata (such as JNDI resource references or database entries for example), the change might be lost when you migrate.
When Use Metadata From Binaries is set to true, the administrative code only updates the metadata in the binary EAR file. This option is not supported in a mixed cell; therefore, it is automatically turned to false as part of migration. When this happens, the expanded metadata in the configuration directories take precedence over the values in the binary EAR file. This causes the values from the original EAR file installation to take precedence over any updates that you might have made.
If Version 6.1 does not support a level for which JSP objects are configured, the migration tools recognize the objects in the output and log them.