Abbreviation for Droits Réservés, Derechos Reservados, etc. meaning Rights Reserved.
It's a copyright notice often found on Spanish, Portuguese, Ibero-American, Caribbean and French records usually in place where you'd normally find a writer's credit. Instead of being a credit it actually indicates the missing status of a registered writer.
Please write down in the release notes which tracks are credited with the status indicator.
Please be extremely careful if in some case the abbrevation refers to actual writer's initials.