Document revision date: 15 July 2002

This section briefly describes the MOUNT command qualifiers that are useful for shadow set management. Refer also to the 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.

Detailed examples and descriptions of how to use these qualifiers are included in Section 4.5. In addition to the shadowing-specific qualifiers described in Table 4-1, the /NOASSIST, /SYSTEM, /GROUP, and /CLUSTER qualifiers are also frequently used when mounting shadow sets, as described in Table 4-2 and in Section 4.4.2.

4.4.1 MOUNT Command Qualifiers Specific to Shadowing

The MOUNT command qualifiers described in Table 4-1 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 Section 4.9.4.1 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. 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 will not be 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 will succeed but a write bitmap will not be created. If NOMINICOPY is specified, the shadow set will be mounted but a write bitmap will not be 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 will occur even if you omit /POLICY=MINICOPY[=OPTIONAL]. If a minicopy successfully starts and then fails for some reason, a full copy will be performed. If a minicopy cannot be started and the keyword OPTIONAL was omitted, the mount will fail. If NOMINICOPY is specified, then a minicopy will not be 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 will be 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 will not be checked. This is the same behavior that occurred before the introduction of this qualifier. The volume label of the copy targets will not be 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.

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 will not be 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 will make 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.

4.4.3 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.

4.4.4 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 need only specify 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.

Example 4-3 Using the /CLUSTER Qualifier

$ MOUNT DSA2: /CLUSTER /SHADOW=$6$DIA4: PEAKSISLAND DISK$PEAKSISLAND $ MOUNT DSA2: /SYSTEM/SHADOW=($6$DIA5:,$6$DIA6:) PEAKSISLAND DISK$PEAKSISLAND

4.5 Adding Shadow Set Members

Once a shadow set is created, you can add and remove individual members by mounting or dismounting physical disk devices. The shadowing software allows you to add and remove shadow set members at any time, transparently to user processes or applications running on the system.

4.5.1 Adding a Disk to an Existing Shadow Set

Example 4-4 shows how to add the disk $4$DUA3 to the DSA23 shadow set.

Example 4-4 Adding a Disk to an Existing Shadow Set

$ MOUNT/CONFIRM/SYSTEM DSA23: /SHADOW=($4$DUA9,$4$DUA3) volume-label

The command in Example 4-4 specifies both the currently active shadow set member ($4$DUA9) and the new member ($4$DUA3). Although it is not necessary to include them when mounting additional physical devices, you can specify current shadow set members without affecting their membership state.

Note that when you add volumes to an existing shadow set mounted across an OpenVMS Cluster system, the shadowing software automatically adds the new members on each OpenVMS Cluster node.

4.5.2 Creating a Two-Member Shadow Set and Adding a Third Member

Example 4-5 shows two commands. The first command creates the shadow set with two members; the next adds a third member to that shadow set.

Example 4-5 Creating a Shadow Set and Adding Third Member

$ MOUNT/SYSTEM DSA4: /SHADOW = ($3$DIA7:, $3$DIA8:) FORMERSELF(1) %MOUNT-I-MOUNTED, FORMERSELF mounted on DSA4: %MOUNT-I-SHDWMEMSUCC, _$3$DIA7: (DISK300) is now a valid member of the shadow set %MOUNT-I-SHDWMEMSUCC, _$3$DIA8: (DISK301) is now a valid member of the shadow set $ MOUNT/SYSTEM DSA4: /SHADOW = $3$DIA6: FORMERSELF(2) %MOUNT-I-SHDWMEMCOPY, _$3$DIA6: (DISK302) added to the shadow set with a copy operation

1. A shadow set is created whose virtual unit name is DSA4. The member disks are $3$DIA7 and $3DIA8.
2. The disk $3$DIA6 is mounted systemwide in the shadow set identified by virtual unit DSA4. The shadow set now includes three shadow set members: $3$DIA6, $3$DIA7, and $3$DIA8. In this example, when you add $3$DIA6 after the shadow set already exists, the added volume becomes the target of a copy operation.

When you add a disk to an existing shadow set, a copy operation is necessary. Volume shadowing automatically performs the copy operation, unless you use the /CONFIRM qualifier or the /NOCOPY qualifier. When you specify the /CONFIRM qualifier, as shown in Example 4-6, the MOUNT command displays the targets of copy operations and requests permission before the operations are performed. This precaution prevents the erasing important data. For more information about copy operations, see Chapter 6.

Example 4-6 Using the /CONFIRM Qualifier

$ MOUNT/CONFIRM DSA23: /SHADOW=($1$DUA4:,$1$DUA6:) SHADOWVOL (1) %MOUNT-F-SHDWCOPYREQ, shadow copy required Virtual Unit - DSA23 Volume Label - SHADOWVOL (2) Member Volume Label Owner UIC (3) $1$DUA6: (LOVE) SCRATCH [100,100] Allow FULL shadow copy on the above member(s)? [N]: NO (4) $

1. This command instructs MOUNT to build a shadow set with the specified devices and to prompt for permission to perform any copy operations.
2. Because a copy operation is necessary, the virtual unit name and the volume label are displayed.
3. The display also includes the physical device name, the volume label, and the volume owner of the potential shadow set member that requires the copy operation.
4. A response of No causes MOUNT to quit without mounting or copying.

When you specify more than one disk, the shadowing software automatically determines the correct copy operation to perform in order to make shadow set members consistent with each other (see Section 6.2 for details). The Mount utility interprets information recorded on each member to determine whether a member requires a copy operation, a merge operation, or no copy operation. If you are not sure which disks might be targets of copy operations, you can specify the /CONFIRM qualifier or the /NOCOPY qualifier as a precaution against overwriting important data when you mount a disk. With the /NOCOPY qualifier, you disable the copy operation.

Example 4-7 shows how to use the /NOCOPY qualifier to check the status of potential shadow set members before any data is erased.

Example 4-7 Using the /NOCOPY Qualifier

$ MOUNT/NOCOPY DSA2: /SHADOW=($1$DUA4:,$1$DUA6:,$1$DUA7:) - _$ SHADOWVOL DISK$SHADOWVOL (1) %MOUNT-F-SHDWCOPYREQ, shadow copy required %MOUNT-I-SHDWMEMFAIL, DUA7: failed as a member of the shadow set %MOUNT-F-SHDWCOPYREQ, shadow copy required (2) $ MOUNT/COPY(3) DSA2: /SHADOW=($1$DUA4:,$1$DUA6:,$1$DUA7:) - _$ SHADOWVOL DISK$SHADOWVOL %MOUNT-I-MOUNTED, SHADOWVOL mounted on _DSA2: %MOUNT-I-SHDWMEMSUCC, _$1$DUA4: (VOLUME001) is now a valid member of the shadow set %MOUNT-I-SHDWMEMSUCC, _$1$DUA6: (VOLUME002) is now a valid member of the shadow set %MOUNT-I-SHDWMEMCOPY, _$1$DUA7: (VOLUME003) added to the shadow set with a copy operation (4)

1. This command instructs MOUNT to build a shadow set, with the specified devices, but only if a copy or merge operation is not required.
2. MOUNT did not build the shadow set because the specified disk, loaded on device $1$DUA7, required a copy operation. At this point you can verify that the volume in device $1$DUA7 does not contain any useful data.
3. If the device does not contain valuable data, you can reenter the MOUNT command and include the /COPY qualifier. This command instructs MOUNT to mount a shadow set and to proceed with the necessary copy or merge operation.
4. The shadow set is successfully mounted. The $1$DUA7 device is currently the target of a copy operation; it will attain full shadow set membership when the copy operation completes.

If a shadow set is already mounted on one or more nodes in an OpenVMS Cluster system, the /SHADOW qualifier is not required when you mount the same shadow set on other nodes in the cluster. For example, if DSA42 is already mounted in the cluster when a new node is brought into the cluster, you can use the following command to mount DSA42 on the new node:

$ MOUNT/SYS DSA42: volume-label logical-name

Upon receiving this command, the volume shadowing software creates the virtual unit on the new node with the same members that currently exist in the cluster.

4.6.1 Reconstructing a Shadow Set With /INCLUDE

Example 4-8 Reconstructing Shadow Sets With /INCLUDE

$ MOUNT /SYSTEM DSA4/SHAD=($4$DIA1,$4$DIA2,$4$DIA3) NEWDISK(1) %MOUNT-I-MOUNTED, NEWDISK mounted on _DSA4: %MOUNT-I-SHDWMEMSUCC, _$4$DIA1: (DISK01) is now a valid member of the shadow set %MOUNT-I-SHDWMEMCOPY, _$4$DIA2: (DISK02) added to the shadow set with a copy operation %MOUNT-I-SHDWMEMCOPY, _$4$DIA3: (DISK03) added to the shadow set with a copy operation $ DISMOUNT DSA4(2) $ $ MOUNT DSA4:/SYSTEM/SHAD=$4$DIA1 NEWDISK/INCLUDE(3) %MOUNT-I-MOUNTED, NEWDISK mounted on _DSA4: %MOUNT-I-SHDWMEMSUCC, _$4$DIA1: (DISK01) is now a valid member (4) of the shadow set %MOUNT-I-AUTOMEMCOPY, _$4$DIA2: (DISK02) automatically added (4) to the shadow set %MOUNT-I-AUTOMEMCOPY, _$4$DIA3: (DISK03) automatically added (4) to the shadow set

1. This is the original MOUNT command that created the shadow set represented by DSA4. The shadow set consists of three shadow set members: $4$DIA1, $4$DIA2, and $4$DIA3.
2. After all copy operations have completed, the DISMOUNT command dissolves the shadow set.
3. The /INCLUDE qualifier triggers the MOUNT command to reconstruct the shadow set back to the way it was before the shadow set was dissolved. The MOUNT command must specify the original virtual unit name (DSA4) and at least one of the original shadow set members ($4$DIA1). The Mount utility reads the membership list on $4$DIA1 (specified in the MOUNT command) to determine that $4$DIA2 and $4$DIA3 are also members of the shadow set.
4. Because the shadow set was properly dismounted, the shadow set members are in a consistent state. The MOUNT status messages indicate that the shadow set devices are added back into the shadow set without the need for copy operations.

Occasionally, you will need to mount a physical shadow set member as a nonshadowed disk. By default, when a shadow set member is mounted outside a shadow set, the Mount utility automatically write-locks the disk. This provides a safeguard against accidental modification, thereby allowing the disk to be remounted into a shadow set at a later time.

To override this default behavior, include the /OVERRIDE=SHADOW_MEMBERSHIP qualifier on the MOUNT command as shown in the following example:

$ MOUNT/OVERRIDE=SHADOW_MEMBERSHIP $4$DUA20: WORKDISK

This command ignores shadow set membership status and mounts a former shadow set member on $4$DUA20 as a nonshadowed disk with write access.

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