The DCL commands DISMOUNT
and MOUNT are used for creating write bitmaps. The MOUNT command
is used for starting a minicopy operation using a write bitmap (see
Starting a Minicopy Operation).
Creating a Write Bitmap With DISMOUNT To create a write bitmap, you must specify the /POLICY=MINICOPY[=OPTIONAL]
qualifier with the DISMOUNT command. If you specify /POLICY=MINICOPY=OPTIONAL,
a write bitmap is created if there is sufficient memory. The disk
is dismounted, regardless of whether a write 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 write 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 write bitmap, the dismount fails.
Creating a Write Bitmap With MOUNT You can create a write 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 write 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 write bitmap is not created.