HP Volume Shadowing for OpenVMS: OpenVMS Version 8.4 > Chapter 7 Using Minicopy for Backing Up Data (Integrity servers and Alpha)

Creating Bitmaps

The DCL commands DISMOUNT and MOUNT are used for creating bitmaps. The MOUNT command is used for starting a minicopy operation using a bitmap (see “Starting a Minicopy Operation ”).

Creating a Bitmap With DISMOUNT

To create a bitmap, you must specify the /POLICY=MINICOPY[=OPTIONAL] qualifier with the DISMOUNT command. If you specify /POLICY=MINICOPY=OPTIONAL, a bitmap is created if there is sufficient memory. The disk is dismounted, regardless of whether a bitmap is created.

The following example shows the use of the POLICY=MINICOPY=OPTIONAL qualifier with the DISMOUNT command:

$ DISMOUNT $4$DUA1 /POLICY=MINICOPY=OPTIONAL

This command removes $4$DUA1 from the shadow set and starts logging writes to a bitmap, if possible.

If you specify /POLICY=MINICOPY only (that is, if you omit =OPTIONAL) and there is not enough memory on the node to create a bitmap, the dismount fails.

Creating a Bitmap With MOUNT

You can create a bitmap with the MOUNT command under the following conditions:

  • The shadow set that was previously mounted was correctly dismounted.

    A multiple member shadow set must have been mounted before on the same node, on another node in the same cluster, or on another node outside the cluster.

  • The shadow set is not currently mounted on any other node in the cluster (if the node on which you are mounting the shadow set is in a cluster).

  • When you mount the shadow set, you mount it minus one member.

  • You specify the /POLICY=MINICOPY[=OPTIONAL] qualifier to the MOUNT command.

The bitmap created with this command is used for a minicopy operation when you later mount one of the former members of the shadow set into the set.

If you specify the /POLICY=MINICOPY=OPTIONAL qualifier and the shadow set is already mounted on another node in the cluster, the MOUNT command succeeds but a bitmap is not created.