The University of California operates the largest academic library system in the world. It manages more than 40.8 million print volumes in 100 libraries on ten campuses. The purpose of these libraries is to assist research and instruction on the University of California campuses. While each campus library is separate, they share (through the UC library system) facilities for storage, computerized indexing, digital libraries and management. Historically, each campus maintained its own library catalog and simultaneously participated in the systemwide union catalog, Melvyl. On July 27, 2021, all ten campuses went live with UC Library Search, a unified systemwide library catalog based on the Ex Libris Alma/Primo platform. The UC libraries also manage a digital library, the California Digital Library or CDL. They also hold special collections and electronic archives of research documents. Special collections include historical archives on California history, federal depositories, law libraries, specialized collections for medical and scientific research, and a series of periodicals. A major concern of the library system is the rising cost of scientific journal subscriptions, and the costs of renting article databases. The library is leading an effort to publish science research online in a persistently-available electronic format, primarily through a digital repository called the eScholarship repository. The physical collections are scattered across the UC campuses. Their collections and stand-alone library buildings are listed below. In the 1980s, to relieve overcrowding in existing on-campus library buildings, the UC system constructed two regional library facilities: the Northern Regional Library Facility at UC Berkeley's Richmond Field Station (opened 1982), and the Southern Regional Library Facility on the western edge of the UCLA campus (opened 1987). As of 2019, Northern Regional Library Facility is home to 7.4 million volumes, while Southern Regional Library Facility is home to 6.5 million. Each facility receives items from all UC campuses in its respective region of the state, and has climate controls and high-density stacks. Items are shelved two deep and are arranged in a sequence that results in efficient use of space (but is not quite as intuitive as traditional library indexing systems). As a result, casual browsing is prohibited, and the shelves are accessible only by library clerks trained to retrieve and put back items properly. Users must page materials to an on-site reading room or to a library at their home campus. List of collections by campus Berkeley (18 university libraries and 11 affiliated libraries—including Law) Doe