dark archives

n. (also dark archive) a repository that stores archival resources but is accessible only to its custodian

Notes

When resources in a dark archives become accessible, they are no longer considered dark. In some cases, records in a dark archives are also accessible to their creators. The term dark archives is also used in libraries for collections of online serial publications and databases that are held by an organization other than the publisher and kept in case they are no longer available from the publisher.