Research into the lifespan of both magnetic and optical media has been conducted. The overwhelming conclusion from this research is that even though magnetic media can be safe for 5-10 years and optical media may survive as long as 30, technology changes much more quickly. Digital media are far more likely to become unreadable as a result of changing technology than they are through media degradation. These diskettes are completely unreadable by PC machines, and can only be accessed on networked Amstrads very rare indeed in 1997. If archaeologists had refreshed their data from 3 inch Amstrad diskettes to 5.25 inch diskettes and then to 3.5 inch diskettes, that digital data would still be accessible and safe.
Data migration is even more important than data refreshment.
Migration is the act of copying digital information from one format or structure into another. One example is copying old flat-field database files into a newer relational database. The functionality of a flat-field database can be maintained in a relational database structure, but without migration the improvements in data handling and retrieval which have led to the widespread acceptance of relational databases would not be drawn upon. Even though CAD packages allow data to be exported in a standard format called DXF , each programme in fact creates DXF files differently. The unwary can find that without careful migration much of the original information is lost when creating a new file.