Technical data

NFS Client
21.4 Mounting Files and Directories
If you specify background mounting, you should also use the /RETRIES qualifier
with a small nonzero number. This qualifier sets the number of times the
transaction itself should be retried. Specify background mounting, along
with the desired delay time and retry count parameters, with the qualifier
/BACKGROUND=[DELAY:OpenVMS_delta_time,RETRY:n].
For example, the following command attempts to mount in background mode,
on local device DNFS4:, the file system /flyer , which physically resides on host
migration . If the mount fails, the NFS client waits 1 minute and then retries the
connection up to 20 times. For example:
TCPIP> MOUNT DNFS4: /HOST="migration" /PATH="/flyer" -
_TCPIP> /BACKGROUND=(DELAY:00:01:00, RETRY:20) /RETRIES=4
If you use the /BACKGROUND qualifier, Compaq strongly recommends that you
also use the /RETRIES qualifier specifying a nonzero value. If you use the default
value for /RETRIES (zero), the first mount attempt can never complete except by
succeeding, and the process doing the mount will hang until the server becomes
available.
21.4.4 Overmounting
Overmounting allows you to mount another path onto an existing mount point.
Specify overmounting with the /FORCE qualifier. The client dismounts the
original mount point and replaces it with a new one.
Mounting a higher or lower directory level in a previously used path is also an
overmount. For example, an overmount occurs when you execute two MOUNT
commands in the following order:
TCPIP> MOUNT DNFS123:[USERS.MNT] /HOST="robin" /PATH="/usr"
%DNFS-S-MOUNTED, /usr mounted on _DNFS123:[USERS.MNT]
TCPIP> MOUNT DNFS123:[USERS.MNT] /HOST="robin" /PATH="/usr/tern" /FORCE
%DNFS-S-REMOUNTED, _DNFS123:[USERS.MNT] remounted as /usr/tern on ROBIN
The second MOUNT command specifies a lower level in the server path. This
constitutes another path name and qualifies for an overmount.
21.4.5 Occluded Mounting
Occluded mounting allows you to mount a file system onto a client mount point
that is higher or lower in the directory structure than an existing, active mount.
This is different from overmounting because dismounting does not occur. Instead,
the client occludes (hides from view) the subdirectories that are added to or
dropped from the original mount specification when you perform a directory
listing.
Specify the /FORCE qualifier with an occluded mount.
In the following example, the mount point specification was backed up
one subdirectory from the previous one. If you enter the SHOW MOUNT
command, both mounts are visible. However, if you enter DIRECTORY
for DNFS2:[USERS.SPARROW], [.MNT] is no longer visible. To make this
subdirectory visible again, issue the DISMOUNT command to dismount
DNFS2:[USERS.SPARROW].
NFS Client 21–11