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.
The command in
Adding a Disk to an Existing Shadow Set 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.
Creating a Two-Member Shadow Set and Adding
a Third Member Creating a Shadow Set and Adding Third Member shows how to create a two-member
shadow set with the first command and how to add another member
to the shadow set with the second command.
Example 5 Creating a Shadow Set and Adding Third Member
%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-I-SHDWMEMCOPY, _$3$DIA6: (DISK302) added to the shadow set with a copy operation
In this example, the first command creates a shadow set whose
virtual unit name is DSA4. The member disks are $3$DIA7 and $3$DIA8.
The second command mounts the disk $3$DIA6 and adds it to shadow
set DSA4. The shadow set now includes three 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.
Checking Status of Potential Shadow Set Members
With /CONFIRM 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
Using the /CONFIRM Qualifier, the MOUNT command displays the targets of copy
operations and prompts for permission before the operations are
performed. This precaution can prevent the erasure of important
data. For more information about copy operations, see
Ensuring Shadow Set Consistency.
$1$DUA6: (LOVE) SCRATCH [100,100] Allow FULL shadow copy on the above member(s)? [N]: NO $
This command instructs MOUNT to build a shadow set with the
specified devices and to prompt for permission to perform any copy
operations.
Because a copy operation is necessary, the virtual unit name
and the volume label are displayed.
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.
A response of No causes MOUNT to quit without mounting or
copying.
Checking Status of Potential Shadow Set Members
With /NOCOPY 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
Copy Operations 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.
Using the /NOCOPY Qualifier shows how
to use the /NOCOPY qualifier to check the status of potential shadow
set members before any data is erased.
%MOUNT-F-SHDWCOPYREQ, shadow copy required %MOUNT-I-SHDWMEMFAIL, DUA7: failed as a member of the shadow set %MOUNT-F-SHDWCOPYREQ, shadow copy required
$ MOUNT/COPY 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
The first command in this example instructs MOUNT to build
a shadow set, with the specified devices, but only if a copy or
merge operation is not required.
In this example, 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.
If the device does not contain valuable data, you can reenter
the MOUNT command, as shown in this example, and include the /COPY
qualifier. This command instructs MOUNT to mount a shadow set and
to proceed with the necessary copy or merge operation.
The resulting MOUNT status messages show that 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.