From Science Europe Data Glossary
Definition: Migration is the transferring of data to newer environments. It may involve transferring data to new media (if the type of media does not change, the term refreshing is also used), but also converting data to new formats.
Explanation: Migration is an act of information logistics, where the bits and bytes of data may change, but their intended meaning remains constant. It is carried out to preserve the meaning of data over time or to make data (better) accessible through a variety of media.
References: http://en.wikipedia.org/wiki/Digital_preservation; Raymond John Prytherch, Harrod's librarians' glossary and reference book : a directory of over 10,200 terms, organizations, projects and acronyms in the areas of information management, library science, publishing and archive management, (Aldershot, Hants, England ; Burlington, VT : Ashgate, 2005), see: http://www.worldcat.org/title/harrods-librarians-glossary-and-reference-book-a-directory-of-over-10200-terms-organizations-projects-and-acronyms-in-the-areas-of-information-management-library-science-publishing-and-archive-management/oclc/498499718
See also: digital preservation