Migration between versions of Application server versions is not trivial. There are several stakeholders involved in the migration, some of which are:

• Developers think of migration only in terms of migration of the application code.  
• Administrators think of migration only in terms of production run time.
• Product Architects think of migration in terms of the impact on design and product features as well as the product roadmap
• Development Managers think of migration in terms of the cost, risk, and the impact on the (LOBs)

People tend to think of a migration with narrow perspectives. This is because of the limited visibility each individual has into the entire process.  It is like the story of the elephant and the 6 blind men. For most organizations using a version of an application server, upgrading to another version is not difficult, if planned properly.  Therefore, it is critical that adequate planning be done be done in advance, so that the external factors (besides code migration), have minimal impact on the actual upgrade.