Latest MidCOM 2.8 has a feature that has been resurrected from earlier in the series: document locking. The point of locking is to prevent accidental simultaneous editing of a document by multiple users.
When user starts editing a document via datamanager-powered form, the document will be marked as locked for that user. Other users accessing the document will see a notice:
Unlocking permissions can be granted via the Asgard user manager.