Whether it is to modernize existing application via an automated migration process,  develop a new application from scratch or replace existing application with COTS, the following steps will be required to perform such data migration:

• Defining the scope of Database migration  - identify those databases, files or tables that comprise the migration. Additionally this will require decisions to be made with respect to historical or archived data.   
• Understanding Database Structure – a full understanding of the existing database structure is required. Identify existence of any duplicate files/data that may exist within the existing database. Similarly, files or data structures that may already exist within the target environment.
• Data Model Design -  the new Data Model needs to be designed. This design will be influenced by factors such as – preservation of existing application functionality, characteristics of the target environment, the manner in which application code accesses the data, integration with data model that currently exists within the target environment.
• New Database Environment -  if not done so already, the new database environment needs to be setup and the new data structures/tables (DDL’s) incorporated within existing or new Database
• Data Mapping/Data Migration Programs   - a data map of the old to the new data needs to be derived. The Data Migration programs that will move data from the old to the new database need to be built. They should include data migration validation and data cleansing aspects as well. Database recovery programs that can rapidly recover the old database from any point of failure should be provided. 
• Data Migration Process  – the process of migrating the data from the old to the new Database needs to be established. Sample migration runs will be conducted to validate migrated data. Additionally performance estimates need to be made with respect to elapsed time required to migrate 100% of data and associated resources dedicated to this process. The recovery plan needs to be established and tested during the migration sampling phase.

All the above constitute key activities in achieving a successful database migration.