3 Archive versus backup
Backup data is recoverable. Usually, disaster recovery is a task of the administrator to make the data available to the end user via the application. However archived data is always accessible to the end user via search or navigation. This access is read-only, the archived data is immutable, stored in the long term. Backup is short-term data; it changes in sync with the application data.
When we archive data, we usually move the data from an application into an archive system. Since it's moved, it won't get changed anymore.
We don't only use archiving when we want to decommission applications. We can also use archiving to unload some data from the application. In this case, we do not move all the data, just part of it. That’s called live archiving.