Database sharing refers to a general architecture for distributed transaction and database processing. The nodes of a database sharing system are locally coupled via
a high-speed interconnect and share the common database at the disk level ("Shared Disk"). We discuss system functions requiring new and coordinated solutions for database
sharing. In particular, the most relevant alternatives for concurrency and coherency control are classified and surveyed. We consider the techniques used in existing
database sharing systems as well as algorithms proposed in the literature. Furthermore, we summarize previous performance studies on database sharing. Related concurrency and coherency control schemes for workstation/server database systems, network file systems, and distributed shared memory systems are also discussed.