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Patent Title: Method and apparatus for concurrency control of shared data updates and queries

Assignee: IBM
Patent Number: US5255387
Issue Date: 10-19-1993
Application Number:
File Date:04-27-1990

Abstract: Method and apparatus for shared data update and query operations. Two control fields are associated with each data block of interest. Before any data in shared memory is modified, a value different from the present value is written into one of the shared memory control fields. The shared memory data is then updated. Thereafter, the other shared memory control field is updated to the new value, thus making the values of the shared memory control fields identical once again. During query operations, the data and control fields of interest are copied into in private storage. The values of the control fields in private memory are compared. If the values are equal, the data in private storage is considered to be consistent. Otherwise, the data is considered to be in the process of being updated and the data is ignored until the values of the shared memory control fields become equal.


Link to USPTO

IBM Pledge dated 1/11/2005