Hi,
well ... this is what CP (consistency point) is - just a special kind of snapshot (from TR3002 -
http://media.netapp.com/documents/wp_3002.pdf)
... WAFL avoids the need for file system consistency checking after an unclean shutdown by creating a special Snapshot called a consistency point every few seconds ...
but time is not the only cause of CP creation - other are log full, data change high enough and ... snapshot creation
(more can be found here - NOW account required -
https://kb.netapp.com/support/index?page=content&id=3012539)
So every snapshot creation gets NetApp WAFL into CP state. NDMP backup creates its own snapshot (or uses designated snapshot - can be set using VIRTUALFSMAPPING) - so using NDMP or any other technique backing up the snapshot is equivalent.
There is one thing we have to keep in mind - there is filesystem consistency (this is what CP does) and application consistency of the file - this cannot be done without application integration no matter what snapshot technology you use (VSS, LVSA, NetApp, ZFS ....).
File locks are not kept in the snapshot (they are related to active filesystem - kept in the memory of NetApp filer) - snapshot is just collection of pointers to the disk blocks - so if you read the snapshot, there is no locked file there - everything can be backed up.
Application consistency of the file cannot be guaranteed - question is if it makes any difference - even if you have your fileserver on the Windows machine (with TSM client on it) and use OFS, you do not get better results.
Long story short - I would not be afraid of any method you choose - just have in mind NDMP has its limitations and is no "silver bullet".
Harry