Archiving is actually a 'royal' discipline of data storage. Among others it means, that the demand on archiving is permanent availability of data. Because the prize of information and demand on its availability decreases during the information lifetime, there is the thought of automating the migration of information processes among all different kinds of storage units so the prize of archive would be as effective as possible.
In practice it means that the information transfers on the basis of defined rules among very fast (but size-limited and expensive) storage units and capacity-oriented storage. These processes are usually called as HSM, ILM, DLM and others.