Technology upgrades pertain to software release upgrades of database or application infrastructure, reconfiguration of data storage, or controlled introduction of commercial off the shelf capabilities into existing configurations, such as setting up replication, altering LDAP configuration or changing security. Technology upgrades involve minimal or no functional changes to the data or applications.
Migrations involve change of technology, e.g. between DB2, Teradata or Oracle, and entail data conversions, restructuring of data, and refactoring of how functionality is mapped to available software/DBMS features to best exploit the new architecture. Unless there is specific advantage, it is preferable to avoid combining functional enhancement with migrations.