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Creating Write Bitmaps  



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 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.


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