Migrating applications across platforms

We often require to migrate applications from one platform (OS/hardware) to an other platform - either as part of a portfolio rationalization program or because the current platform is reaching its EOL. For e.g. migrating Java apps from Solaris/SPARC to Linux/IBM Power, etc.
During such migrations, it is essential to have a well documented plan covering all the aspects, so that we do not miss anything. Listed below is a brief set of points that must be included in the brainstorming discussions during the planning phase.

1. Migration of the Runtime environment: For e.g. miration of the Java runtime from Solaris to Linux. There are many JRE's available on Linux and we need to select the appropriate one.
2. Migration of the Application Infrastructure: The application may require a webserver, application server, a Message queue, etc. These infrastructure components would need to be ported to the target platform or other alternatives selected.
3. Migration of application code: Does the code need to be recompiled/linked on the target platform? Was the application using any platform specific API for performance?
4. Migration of application configuration: What configuration needs to change on the target platform? e.g. file paths, endian-ness, max-memory settings, thread pool settings, etc.
5. Migration of development environment: Would it be required to migrate the development environment? Will the same IDE work? IDE-Runtime integration issues, etc.
6. Migration of Build and Deployment process: Need to change build scripts - ANT, Maven, Shell scripts, etc.

Also it makes sense to leverage the expertise of the target platform vendor during the migration exercise. For e.g. IBM, HP, SUN, RedHat, Novell, etc. all have guidelines, recommendations and migration kits for migrating from a target platform to their platform.