Under the NFS version 2 and version 3 protocols, the z/OS NFS server strives to be as stateless as possible; that is, it tries to work correctly without maintaining any state information about any of its clients. However, a failure of the server causes cached writes to be lost, some attributes to be reset, and file handles to become stale, or not valid.

With the NFS version 4 protocol, the z/OS NFS server maintains state information for some client operations, to prevent such loses.