For Filer CIFS, when concurrently several clients open the same file, then thees clients (all these clients have write access on the file) try to modify and write to this file differently almost at the same time. What will happen to this file? Which client will have the final right to have the file modified?
Generally speaking, the application instance that writes last within a set of bounds will get to take home the cheese, but this is precisiely the type of thing that concurrency controls exist to manage. If multiple instances of an application need to share/modify a single file in a cooperative manner, the app should be using Win32 CreateFile() share modes, and functions like LockFile() & LockFileEx() to avoid deadlocks, file corruption, and any of the other nasty things that can happen when apps that weren't designed to share common file spaces try and do so.
Data ONTAP supports all of these standard mechanisms on the Windows/CIFS side, and even extends them across into the NFS space using a technology called SecureShare. The protection mechanisms are designed to preserve data integrity by ensuring that when locking semantics conflict between the different locking protocols/paradigms, the "path taken" will be the behaviour that would prevent corruption, or potential corruption from occuring.
Keith