The primary purpose of this material is to provide information required to plan and execute a successful migration between different versions of WebSphere Application Server. The goal is to provide a central set of information and references to enable customers of WebSphere Application Server to do this migration themselves without requiring assistance. There has been significant improvement over time in the area of WebSphere Application Server migration, but there are still some technical aspects involved in any migration scenario. These technical aspects can be addressed easier, and with reduced risk, if understood and addressed early. The overall process will always need careful planning and execution no matter how trivial the technical aspects might become for compatibility of applications themselves.
There are different migration scenarios. Migration scenarios are defined based on what combination of WebSphere Application Server versions are being migrated. There are different factors to consider based on what the “from” and “to” versions are that are being migrated. Each migration scenario is unique.
via IBM – Knowledge Collection: Migration planning for WebSphere Application Server.