Understanding file locking between protocols

About file locking

File locking is a method used by client applications to prevent a user from accessing a file previously opened by another user. How Data ONTAP locks files depends on the protocol of the client.

If the client is an NFS client, locks are advisory.
If the client is a CIFS client, locks are mandatory.

Which NFS operations fail

Because of the difference between the locks, some attempts by an NFS client to access a file opened by a CIFS application fail.

The following occurs when an NFS client attempts to access a file locked by a CIFS application:

File manipulation operations, such as rm, rmdir, and mv, by an NFS client on a file opened by a CIFS client application can cause the NFS application to fail. This only occurs in mixed or NTFS qtrees.
NFS read and write operations will be denied by CIFS deny-read and deny-write open modes, respectively.
NFS write operations will also fail when the written range of the file is locked with an exclusive CIFS bytelock.

Exception

One exception to the enforcement of locks set by CIFS clients on the filer is when the filer runs the dump command. The dump command ignores the file lock set by a CIFS client that prevents read access to parts of a file or the entire file. Ignoring the file lock enables the filer to back up all files.

Note
If an attempt by an NFS client to access a file opened by a CIFS application fails, you can use the cifs terminate command to disconnect the session that has the open file that you want to access. You can determine which session has that file open using the cifs sessions * command or Server Manager. If you terminate a CIFS session, the client may receive errors.