Appian Records Locking Mechanism

To prevent multiple user access and edit, add a new column in the table, isLocked. When a user opens the form through the process model, pertaining to that record, set isLocked=true, also, and just before the end node of the process, mark isLocked=false. Next, when a user access the same form, check first if isLocked=true, if it is, disallow the user, else, repeat the previous logic.

This is one of the ways to implement locking at DB level, there are other methods to do this as well. 

To prevent multiple user access and edit, add a new column in the table, isLocked. When a user opens the form through the process model, pertaining to that record, set isLocked=true, also, and just before the end node of the process, mark isLocked=false. Next, when a user access the same form, check first if isLocked=true, if it is, disallow the user, else, repeat the previous logic.

This is one of the ways to implement locking at DB level, there are other methods to do this as well. 

Keep in mind that you need some way to "unlock" records manually.