Major astronomical facilities generally use a large number of machine-readable catalogs and data sets. These are requested over a long period of time, usually by individual staff members who seldom request data through their library services. An important drawback of this procedure is that the same catalogs are often requested by different persons at the same institute, thus requiring a duplicate effort on the part of the service organization (usually the data centers) and longer than necessary delays for the persons requesting data. It is suggested that libraries at major facilities build collections of important data sets and maintain library catalogs of these collections for use by staff astronomers. This paper discusses simplified and efficient methods of building such collections and details possible ways of storing and retrieving particular catalogs easily when they are required by staff members.