In NFS version 2 and version 3, the z/OS NFS NLM allows a client on the host to lock range of bytes or an entire file on the z/OS NFS server. The two types of locks that the client host uses are monitored locks and non-monitored locks.

The z/OS NFS NLM supports only advisory locking. Advisory locking is when the operating system keeps track of which files have been locked by which process, but does not prevent a process from writing to a file that is locked by another process. This means that a process can ignore an advisory lock if the process has adequate permission.