Data Migration
Data Migration is the process of transferring data from one system to another while changing the storage, database or application. In reference to the ETL (Extract-Transform-Load) process, data migration always requires at least Extract and Load steps.
Typically data migration occurs during an upgrade of existing hardware or transfer to a completely new system. Examples include: migration to or from hardware platform; upgrading a database or migrating to new software; or company-mergers when the parallel systems in the two companies need to be merged into one. There are three main options to accomplish data migration:
Merge the systems from the two companies into a brand new one
Migrate one of the systems to the other one.
Leave the systems as they are but create a common view on top of them - a data warehouse.