The same dataset may be accessed by several users at the same time. The system checks contending data access attempts, so that modifications of a dataset by a user would not disrupt the activity of other users (contention checks).
The Routes system uses two methods to control users contending for data:
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the first-come, first-served contention control mode: if a user accesses a dataset, the data is locked for editing when other users access it. When the original user no longer needs the data locked for editing, he/she saves the modifications and the data is automatically unlocked. If a user wishes to modify an item locked by another user, a warning message notifies him/her that the data is locked, and it is displayed in a read-only mode.
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the free-for-all contention control mode: this contention control mode does not lock data. When a user saves dataset modifications, the system checks for contending modifications by another user; if a contention is detected, it feeds back an error message which allows the user to refresh server data.
