Archiving research data means storing it for a long term in a fixed state. Normally you do so in a data archive or a repository. The difference between the two is that, in contrast to an archive, a repository has mechanisms for finding and retrieving the data, e.g. through a data catalogue and a download option. The retention period in an archive can differ. A minimum of 10 years is currently the norm. Note that the sustainability of the data over time can be hampered by the file formats used. The (re)usability of the data is strongly improved by adding descriptions of the data (metadata).