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.