Because transactions lock all records they touch, 4D Backup waits for transactions to complete before it begins a backup. Once 4D Backup has started a new user cannot log into the database until it is complete. These two factors combined can potentially lock users out of the database indefinitely.

Example: One user leaves their machine in a detail form which has a transaction, 4D backup begins and waits for the completion of the transaction which does not happen because the user has left their machine.