This
section briefly describes the MOUNT command qualifiers that are useful
for shadow set management. See also the HP OpenVMS System
Management Utilities Reference Manual for complete information
about these and other DCL commands.
You must use the /SHADOW qualifier when you create
a new shadow set or when you add a member to an existing shadow set.
You can also use the optional qualifiers described in Table 4-1 and in Table 4-2. These qualifiers require the VOLPRO and OPER privileges,
or your user identification code (UIC) must match the owner UIC of
the volume being mounted. To mount a shadow set throughout the system,
you must also have the SYSNAM privilege. In addition, the MOUNT/POLICY=[NO]MINICOPY[=OPTIONAL]
command requires the LOG_IO privilege.
Table 4-1 describes the MOUNT command qualifiers that are specific to shadowing.
Table 4-1 MOUNT Command Qualifiers (Shadowing Specific)
Qualifier
Function
/[NO]CONFIRM
Controls whether the
Mount utility issues a request to confirm a copy operation when mounting
a shadow set. The default is /NOCONFIRM.
/[NO]COPY
Enables or disables copy
operations on physical devices named when mounting or adding to a
shadow set. The default is /COPY.
/[NO]INCLUDE
Automatically mounts
and reinstates a shadow set to the way it was before the shadow set
was dissolved. The default is /NOINCLUDE.
/OVERRIDE=
NO_FORCED_
ERROR
Directs the Mount utility to proceed with shadowing,
even though the device or controller does not support forced error
handling. Using unsupported SCSI disks can cause members to be removed
from a shadow set if certain error conditions arise that cannot be
corrected, because some SCSI disks do not implement READL and WRITEL
commands that support disk bad-block repair. If the SCSI device does
not support READL and WRITEL commands, the SCSI disk class driver
sets a NOFE (no forced error) bit in a System Dump Analyzer display.
See “Using SDA to Obtain Information About Third-Party SCSI Devices” for
more information.
/OVERRIDE=
SHADOW_
MEMBERSHIP
Mounts a former shadow set member and zeroes the
disk's shadow set generation number so that the disk is no longer
marked as having been a member of the shadow set.
/POLICY=
[NO]MINICOPY [=OPTIONAL]
Controls
the setup and use of the shadowing minicopy function. This qualifier
requires LOG_IO privilege.
The meaning of [NO]MINICOPY[=OPTIONAL]
depends on the status of the shadow set. If the shadow set is not
mounted, either on a standalone system or on any cluster member, and
MINICOPY=OPTIONAL is specified, the shadow set is mounted and a write
bitmap is created. (A write bitmap enables a shadowing minicopy operation.)
MOUNT/POLICY=MINICOPY[=OPTIONAL] must be specified on the initial
mount of a shadow set, either on a standalone system or in a cluster,
to enable the shadowing minicopy operation.
The OPTIONAL
keyword allows the mount to continue, even if the system was unable
to start the write bitmap. A bitmap could fail to start properly because
of an improperly dismounted shadow set, a shadow set that requires
a merge operation, or various resource problems. If the OPTIONAL keyword
is omitted and the system is unable to start the write bitmap, the
shadow set is not mounted.
If you specify /POLICY=MINICOPY=OPTIONAL
and the shadow set was already mounted on another node in the cluster
without this qualifier and keyword, the MOUNT command succeeds but
a write bitmap is not created.
If NOMINICOPY is specified,
the shadow set is mounted but a write bitmap is not created.
If a former member of the the shadow set is returned to the
shadow set, which has minicopy enabled, then a minicopy is started
instead of a full copy. This is the default behavior and occurs even
if you omit /POLICY=MINICOPY[=OPTIONAL]. If a minicopy successfully
starts and then fails for some reason, a full copy is performed.
If a minicopy cannot be started and the keyword OPTIONAL was
omitted, the mount fails.
If NOMINICOPY is specified,
then a minicopy is not performed, even if one is possible.
/POLICY=
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 command to take effect. The proposed
members are either specified in the command line or found on the disk
by means of the /INCLUDE qualifier. The behavior, without this qualifier,
is that if one or more members is not accessible for any reason (such
as a connectivity failure), then the virtual unit is created with
the members that are accessible. This option is especially useful
in the recovery of disaster-tolerant clusters because it ensures that
the correct membership is selected after an event.
/POLICY=
VERIFY_LABEL
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 by mistake. If you plan to use VERIFY_LABEL,
then before using this qualifier you must either initialize the disk
to be added to the set with the label SCRATCH_DISK, or specify a label
for the disk with the command SET VOLUME/LABEL.
The default
behavior is NOVERIFY_LABEL, which means that the volume label of the
copy targets is not checked. This is the same behavior that occurred
before the introduction of this qualifier. The volume label of the
copy targets is not checked.
/SHADOW=
(physical-device-name[:][,...])
Directs the Mount utility to bind the specified physical devices
into a shadow set represented by the virtual unit named in the command.
CAUTION: Do not use the /OVERRIDE=IDENTIFICATION or /NOMOUNT_VERIFICATION
qualifiers when mounting shadow sets. Using either of these qualifiers
can result in loss of data.
If you mount a shadow set with the /OVERRIDE=IDENTIFICATION
qualifier, individual shadow set members start with different volume
labels, which can cause a volume to lose data.
If you specify the /NOMOUNT_VERIFICATION qualifier,
the shadow set becomes unusable at the first state change of the shadow
set.
Additional MOUNT Command Qualifiers Used for Shadowing
The MOUNT command qualifiers described in this
section are not specific to shadowing but can be very useful when
creating shadow sets. These additional qualifiers are described in Table 4-2 and in the examples
that follow.
Table 4-2 Additional MOUNT Command Qualifiers (Not Shadowing Specific)
Qualifier
Function
/NOASSIST
Successfully mounts a
shadow set if at least one of the devices included in the MOUNT command
is available for mounting. In the absence of this qualifier, if one
of the devices specified to be mounted is not available for mounting,
the shadow set is not mounted.
/SYSTEM
Makes the volume available
to all users on the system. Use this qualifier when you add a disk
to an existing shadow set. If the /CLUSTER qualifier was used when
the shadow set was created, the use of /SYSTEM makes the new member
of the shadow set available to all nodes in the cluster that already
have the shadow set mounted.
/GROUP
Makes the volume available to all users with the
same group number in their UICs as the user entering the MOUNT command.
You must have GRPNAM and SYSNAM user privileges to mount group and
system volumes.
/CLUSTER
Creates the virtual unit automatically
on every node in the cluster on which shadowing is enabled. Use this
qualifier if the shadow set is to be accessed across the cluster.
You must have the SYSNAM privilege to use this qualifier. Using /CLUSTER
automatically includes the /SYSTEM qualifier, making the shadow set
available to all users on the system.
Creating a Shadow Set With /NOASSIST
You may occasionally find it useful to specify
the /NOASSIST qualifier on the MOUNT command. For example, you can
use the MOUNT/NOASSIST command in startup files to avoid failure of
a MOUNT command when a device you specify in the command is not available.
The /NOASSIST qualifier can be used in startup files because operator
intervention is impossible during startup.
The MOUNT/NOASSIST qualifier can successfully
mount the shadow set as long as at least one of the devices included
in the MOUNT command is available for mounting. Example 4-2 shows an example of the
/NOASSIST qualifier and the resulting messages when one of the members
included in the command is not available for mounting.
Example 4-2 Using the /NOASSIST Qualifier
$MOUNT/SYS DSA65:/SHADOW=($4$DIA6,$4$DIA5) GALEXY/NOASSIST%MOUNT-I-MOUNTED, GALEXY mounted on _DSA65:%MOUNT-I-SHDWMEMSUCC, _$4$DIA6: (READY) is now a valid member of the shadowset%MOUNT-I-SHDWMEMFAIL, $4$DIA5 failed as a member of the shadow set-SYSTEM-F-VOLINV, volume is not software enabled
Even though device $4$DIA5 is not available for
mounting, the MOUNT command continues to create the shadow set with
$4$DIA6 as its only member. If the command did not include the /NOASSIST
qualifier, the MOUNT command would not mount the shadow set.
Creating a Shadow Set With /SYSTEM and With /CLUSTER
When you create a shadow set, you must specify
either the /SYSTEM qualifier or the /CLUSTER qualifier, or both (see Table 4-2) to provide access
for all users on a single system or on a cluster.
In Example 4-3, if the shadow set (identified by its virtual unit name DSA2) is
not currently mounted, the first command creates a shadow set with
one shadow set member; the second command adds two more members to
the same shadow set. An automatic copy operation
causes any data on the second and third volumes to be overwritten
as the shadow set members are added.
In the second MOUNT command, you have to specify
only the /SYSTEM when you add the $6$DIA5 and $6$DIA6 devices to the
shadow set. Do not use /CLUSTER. These disks are added with the same
status that the shadow set currently has, which in this case is clusterwide
access.
