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.