Data migration
There is a difference between data migration and data integration activities. Data migration is a project by means of which data will be moved or copied from one environment to another, and removed or decommissioned in the source. During the migration (which can take place over months or even years), data can flow in multiple directions, and there may be multiple migrations taking place simultaneously. The ETL (extract, transform, load) actions will be necessary, although the means of achieving these may not be those traditionally associated with the ETL acronym.
Data island
A data island is a data store, such as on a PDA or other computing device, that has non-existent or limited external connectivity. This limits the ability of the user to synchronize with or copy the data to other devices. Though new data can be added to the system, the ability to move that data elsewhere is impractical or impossible. Data islands, in general, contain a very huge set of data relative to its small physical space that it occupies.