Abstract: A method and architecture for sharing data items using a resource sharing facility with a medium level cache accessible to all of the computers which are to share and connected to the computers by fast intersystem links. The resource sharing facility also acts as an ordinary secondary storage controller and in the resource sharing facility the control information and logic is provided which is needed for the mapping of cache data to the secondary storage and vice versa.

Abstract: Heterogeneous computer systems are computer systems with different storage architectures, computer systems with different central processing units (CPUs), computer systems with different disk organization methods, computer systems with different access methods, computer systems that use different controller interfaces etc. These systems share data so that every one of the said computer systems can access the data independently, not relying on services from the others. A single copy of the data is maintained, as opposed to replicated data that is used, in some cases to overcome the same needs. Every system has direct access to the shared data, through the use of emulators that enable applications on every system to use the desired interfaces to the data, disguised as the ordinary local interfaces. An example is the accessing an IBM mainframe's DB2 data base from a UNIX environment.