CHGMDISK to move disks using DDR not CMS COPY

Document ID : KB000014482
Last Modified Date : 14/02/2018
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Question:

When using the VM:Secure command CHGMDISK, why is it doing a DDR rather than a CMS COPY to copy the disk ?

 

Answer:

For the most part, VM:Secure will use DDR rather than CMS COPY to copy a disk unless: 

1. Origin and new disk have different devtype, blksize, disk size 

2. The disk is a VMSECURE service machine disk 

3. You are trying to change the label on the new disk 

We need to ACCESS a disk that will be DDR'd because of what the product does prior to the DDR in querying the disk to help it decide whether to do the DDR among other things. The ACCESS is done early in CHGMDISK due to the call to QRYDISK. That logic is what causes the disk to be accessed. In the end, this access isn't related to the DDR but still is done and that is why we do the RELEASE at the end. Though it is DDR, we have reason to do this access and the release is done in the end.

The ACCESS and RELEASE are done for reasons other than the DDR so that logic won't be changed. There are a lot of other things going on in a CHGMDISK other than the DDR and the ACCESS is required for that processing.