Abstract: A method of data sharing between processors on the same network utilizes en migration for providing a data locking mechanism. A token migrates between the processors for each original data item and its replicas. Only the processor having possession of the token can perform certain operations such as updating and transmitting this updated information to the other processors. Two different queuing arrangements are described for giving up or retaining possession of the token when a processor, not in possession of the token makes a request for the token.

Abstract: A system for updating and reading a data base utilizes a pair of counters ere one counter is incremented prior to an update and the other is incremented following an update. The system permits the updating to take place at any time. By keeping track of the value of the counters the system either inhibits the reading from taking place during the updating if the updating commenced prior to the commencement of the reading or provides information that an updating occurred during the reading if the reading commenced prior to the commencement of the updating. The counters and data base are located within the RAM of a computer. The system has a first application program that gives information to a second application program via these RAM based components.

Abstract: A system for updating and reading a data base utilizes a pair of counters rking in conjunction with registers located within RAM to enable one upon reading the data base to know if a data base record has been added, deleted, or revised. The system also notifies if the data base is being updated on attempting a read process or during the reading. The updating is performed by a writer that is never inhibited from updating the data base.