Upgrading from earlier version of Retain 4 to the current version requires the running of the installer and choosing upgrade. It is recommended to make a backup first.
Retain must have database owner rights to the SQL database it is connected to, for updating the schema and the like.
When updating very large databases (near a terabyte) the upgrade may take considerable time (on the order of a couple of hours). This also requires temporary disk space. If temporary disk space runs out the system may crash and the schema update process will have to be restarted.