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Patent Title: Parent/child subset locking scheme for versioned objects

Assignee: IBM
Patent Number: US5623659
Issue Date: 04-22-1997
Application Number:
File Date:06-07-1995

Abstract: For concurrent access by a plurality of users to a data set in a memory, a computer system first searches for a write lock on a first portion of the data set which the user wishes to access. For no write lock detected, the request is granted by allowing write access to the first portion. A write lock is placed on the first portion of the data set to prevent other users from changing it, while allowing other users read access to the first portion. If a second user wants write access to a second not interesting portion of the data set, the process is similar. A search for a write lock on a second portion of the data set is conducted. If not found, the second user's request for write access to the second portion is granted. A write lock on the second portion is placed to prevent other users from changing the second portion while allowing read access. If a third user wants access to a third portion of the data set wherein the third shares some common elements with the first portion, but has other elements which are not shared, his request will partially granted to the portion of the third portion which is not shared by the first portion. A write lock is placed on the portion of the third portion to which the third user is allowed write access. When a user has finished with his portion of the data set, the write lock is removed and the parent version of the data set is updated.

Notes:

Link to USPTO

IBM Pledge dated 1/11/2005