The Solaris 2 mount(1M) command issues this message whenever it mounts a filesystem that doesn't have NFS locking, such as a standard SunOS 4.1 exported filesytem. Data loss is possible in applications that depend on locking.
On the remote SunOS 4.1 system, install the appropriate rpc.lockd jumbo patch to implement NFS locking. For SunOS 4.1.4, install patch #102264; for SunOS 4.1.3, install patch #100075; for earlier 4.1 releases, install patch #101817.