Technical data

System Management Features

4.13 Volume Shadowing for OpenVMS

On Site A:

$ DISMOUNT /FORCE_REMOVAL= $1$DGA2000:

Once the command has completed, the shadow set will be available for use only

at site A.

On Site B:

$ SET DEVICE /ABORT_VIRTUAL_UNIT DSA42:

Once the command completes, the shadow set status will be

MntVerifyTimeout

Next, issue the following command to free up the shadow set:

$ DISMOUNT/ABORT DSA42:

These steps must be taken for all affected multiple-site shadow sets.

4.13.3 Using INITIALIZE/SHADOW/ERASE to Streamline the Formation of a

Shadow Set

The new /SHADOW qualiﬁer to the DCL INITIALIZE command is available. The

use of the INITIALIZE /SHADOW command to initialize multiple members of a

future shadow set eliminates the requirement for a full copy operation when you

later create a shadow set.

Compaq strongly recommends that you also specify the /ERASE qualiﬁer with the

INITIALIZE/SHADOW command when initializing multiple members of a future

shadow set. Whereas the /SHADOW qualiﬁer eliminates the need for a full copy

operation when you later create a shadow set, the /ERASE qualiﬁer reduces the

amount of time a full merge will take.

If you omit the /ERASE qualiﬁer, and a merge operation of the shadow set is

subsequently required (because a system on which the shadow set is mounted

fails), the resulting merge operation will take much longer to complete.

The INITIALIZE command with the /SHADOW and /ERASE qualiﬁers performs

the following operations:

• Formats up to six devices with one command, so that any three can be

subsequently mounted together as members of a new host-based shadow set.

• Writes a label on each volume.

• Deletes all information from the devices except for the system ﬁles containing

identical ﬁle structure information. All former contents of the disks are lost.

You can then mount up to three of the devices that you have initialized in this

way as members of a new host-based shadow set.

For more information, refer to Volume Shadowing for OpenVMS.

System Management Features 4–25