This section briefly
describes the SYS$MOUNT item codes that are useful for shadow set
management. Refer to the HP OpenVMS System Services Reference Manual for
complete information about SYS$MOUNT, item codes, and other system
services.
MNT$_FLAGS
Item Code The MNT$_FLAGS item code specifies a longword bit vector in
which each bit specifies an option for the mount operation. The
buffer must contain a longword, which is the bit vector.
The $MNTDEF macro defines symbolic names for each option (bit)
in the bit vector. You construct the bit vector by specifying the
symbolic names for the desired options in a logical OR operation.
The following list describes the symbolic names for each shadow
set option:
MNT$M_INCLUDE automatically
reconstructs a shadow set to the state it was in before the shadow
set was dissolved (because of dismounting or system failure). Use
this option when mounting a complete shadow set.
MNT$M_NOCOPY disables automatic
copy operations on all physical devices being mounted or added to a
shadow set. This option prevents accidental loss of data that could
occur if an unintended device is added to the shadow set.
MNT$M_MINICOPY_REQUIRED means that $MOUNT fails
if minicopy has not been enabled on the disk.
MNT$M_MINICOPY_OPTIONAL means
that $MOUNT continues even if minicopy has not been enabled on the
disk.
MNT$M_OVR_SHAMEM allows you to mount former shadow
set members outside of the shadow set. If you do not specify this
option, $MOUNT automatically mounts the volume write-locked to prevent accidental
deletion of data. To specify this option, you must either own the
volume or have the VOLPRO privilege. When you use this option, the shadow set generation number
is erased from the volume. If you then remount the volume in the
former shadow set, $MOUNT considers it an unrelated volume and marks
it for a copy operation.
MNT$M_REQUIRE_MEMBERS controls whether every physical
device specified with the /SHADOW qualifier must be accessible when
the MOUNT command is issued in order for the $MOUNT system service
to take effect.
MNT$M_VERIFY_LABELS requires that any member to
be added to the shadow set have a volume label of SCRATCH_DISK.
This helps ensure that the wrong disk is not added to a shadow set.
If you plan to use VERIFY_LABELS, you must assign the disk a label
first. You can do this either by initializing the disk to be added
to the set with the label SCRATCH_DISK or by specifying a label
for the disk with the SET VOLUME/LABEL command. The default is NOVERIFY_LABEL,
which means that the volume label of the copy targets will not be
checked. This default behavior is the same that occurred prior to
the introduction of this option.
MNT$_SHANAM
Item Code Specifies the name of the virtual unit to be mounted. The
buffer is a 1- to 64-character string containing the virtual unit
name in the format DSAn. This string can also be a logical name;
if it is a logical name, it must translate to a virtual unit name.
An item list must include at least one MNT$_SHANAM item descriptor.
If you are mounting
a volume set containing more than one shadow set, you must include
one MNT$_SHANAM item descriptor for each virtual unit included in
the volume set.
MNT$_SHAMEM
Item Code Specifies the name of a physical device to be mounted into
a shadow set. The shadowing software adds the device to the shadow
set represented by the virtual unit specified in the MNT$_SHANAM
item descriptor. The MNT$_SHAMEM descriptor is a 1- to 64-character
string containing the device name. The string can be a physical
device name or a logical name; if it is a logical name, it must
translate to a physical device name.
An item list must contain at least one item descriptor specifying
a member; this item descriptor must appear after the MNT$_SHANAM
item descriptor.
Points
to Remember When Constructing a $MOUNT Item List Here are some important points to remember when you construct
a $MOUNT item list:
Every item list that mounts a shadow
set must contain at least one item descriptor that specifies the virtual
unit and at least one item descriptor that specifies a member.
The item descriptor that specifies the virtual unit
must come before the item descriptors that specify the members contained
in the shadow set. Then, you can specify any number of members that
are to be represented by that virtual unit by using the MNT$_SHAMEM
item code.
When mounting a volume set, your item list must
contain an item descriptor for each virtual unit. The virtual unit
item descriptor must be followed by item descriptors specifying
the members to be represented by that virtual unit.
When you mount a shadow set, the system determines
whether a device requires a copy or merge operation before it can
join the shadow set. Therefore, you can use the MNT$_SHAMEM item
code to specify any member, regardless of the operation the device
requires.
HP Volume Shadowing for OpenVMS
Creating and Managing Shadow Sets with System... 
