$MOUNT Shadow Set Item Codes
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This section briefly describes the SYS$MOUNT item codes that are useful for shadow set management. See the HP OpenVMS System Services Reference Manual for complete information about SYS$MOUNT, item codes, and other system services.
The MNT$_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 is not checked. This default behavior is the same that occurred prior to the introduction of this option.
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.
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.
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.