Information Modeling and Relational Databases, 2nd Edition

14.9. Data Migration and Query Transformation

Data migration, the fourth phase of reengineering, can sometimes be challenging. When the original database is populated with massive amounts of data, it is typically impractical to convert and renter the data manually into the new database schema. While most DBMSs provide tools to assist with data migration, these tools usually handle only simple data transformations, so you need to write your own transforms to deal with more complex cases. Such data transformations are normally written in SQL, although XSLT could be used if the data is available in XML form.

Once the data migration is completed, any stored queries on the old database need to be recoded to perform equivalent queries on the new databases. ...