This is what AWS has to say: Migration follows following steps:
Phase 1: Migration Preparation and Business Planning
Here you determine the right objectives and begin to get an idea of the types of benefits you will see. It starts with some foundational experience and developing a preliminary business case for a migration. This requires taking your objectives into account, along with the age and architecture of your existing applications, and their constraints. We have partners such as RISC Networks, Atadata, Cloudamize, TSOLogic, and Apptio that have experience in this area.
Phase 2: Portfolio Discovery and Planning
Next, you need to understand your IT portfolio, the dependencies between applications, and begin to consider what types of migration strategies you will need to employ to meet your business case objectives. With the portfolio discovery and migration approach, you are in a good position to build a full business case. If you need help with understanding your IT portfolio, you can work with partners such as RISC Networks, Cloudamize, and Atadata as well as use AWS Application Discovery Service.
Phase 3 & Phase 4: Designing, Migrating, and Validating Application
Here the focus moves from the portfolio level to the individual application level and you design, migrate, and validate each application. Each application is designed, migrated, and validated according to one of the six common application strategies (“The 6 R’s”). Once you have some foundational experience from migrating a few apps and a plan in place that the organization can get behind - it’s time to accelerate the migration and achieve scale. Partners such as Cloudendure, CloudVelox, Atadata, Racemi, and Attuinity can help you here as well as AWS Server Migration Service (SMS) and AWS Database Migration Service (DMS).
Phase 5: Operate
As applications are migrated, you iterate on your new foundation, turn off old systems, and constantly iterate toward a modern operating model. Your operating model becomes an evergreen set of people, process, and technology that constantly improves as you migrate more applications. We have partners such as AppDynamics, NewRelic, and Dynatrace that can help you continue to iterate on your operating model as you move more to the cloud.