From time to time a file system technology or a database system becomes obsolete, is not supported anymore, or there’s a decision to move to a different more modern format. That’s the case of archived material that needs to be re-archived on a new system.
Different database systems, although supporting the same relational concept, may use different types of fields, tables, SQL syntax, and relationship models and thus require mapping of the old format to the new one. This is usually done automatically with dedicated software, but may require manual attending in cases of non normalized systems such as text or old SGML. This process may include validation and configuration as well to fit new business requirements.