In NFS version 2 and version 3, the z/OS NFS NSM is a service that provides applications with information on the status of network host. Each z/OS NFS NSM keeps track of its own "state" and notifies any interested parties of a change in its state.

For correct operation of the z/OS NFS NSM, the client and the server hosts are required to monitor each other. When a lock request is issued by a process running on the client host, the NLM on the client host requests the NSM on the client host to monitor the server host. The client NLM then transmits the lock request to the z/OS NFS NLM on the server. On recept of the lock request the z/OS NFS NLM on the server host will request the z/OS NFS NSM on the server host to monitor the client host. In this way, each host is monitored by the NSM on the other host.