The z/OS NFS server maintains a list of the active mount points in a pair of files called the mount handle data sets on MVS™ also known as the mount handle database (MHDB). The two data sets are used alternately to automatically reestablish the client mount points when the server is started. If the file system is not available, the mount point is not reestablished and the mount failure is recorded in the log data set.

The z/OS NFS server does the cleanup activity during z/OS NFS server shutdown and daily at the cleanup time specified by the restimeout site attribute.

During cleanup time, the z/OS NFS server reads the list and checks all mount points against the retention period specified in the restimeout site attribute. If your mount points are idle longer than the retention period specified in the restimeout site attribute, they are removed. Only the active mount points are reconnected.

If a mount handle is removed by the cleanup activity, the client user might receive the “Stale NFS File Handle” message or some other appropriate message. If so, all the client user needs to do is unmount the stale mount point and mount it again.

NFS Version 4 mount points that were established without specifying the MVSMNT processing attribute are not recorded in the MHDB. However, for NFS Version 4 mount points without the MVSMNT processing attribute, the MHDB is updated with records at z/OS NFS server shutdown that are used solely for diagnostic purposes. At z/OS NFS server restart, the server reviews the diagnostic records and reports the reason why the mount points were not reestablished. This helps diagnose any problems that may occur during a failover.