z/VM: CP Commands and Utilities Reference - z/VM - IBM

DEFINE (Virtual Disk in Storage)
DEFINE (Virtual Disk in Storage)
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DEFine
Authorization
Purpose
Operands
VFB-512
Usage Notes
AS
vdev
BLK
Privilege Class: E, G
198 z/VM: CP Commands and Utilities Reference
nnnnnnn
Use DEFINE to create a virtual disk in storage attached to your virtual machine. A
virtual disk in storage created using this command is temporary, private
(nonshareable), and simulates an FBA minidisk, which is defined in 512-byte blocks.
The virtual disk in storage is destroyed when you detach it or log off.
vdev
AS vdev
is the virtual device number to be assigned to the virtual disk in storage.
nnnnnnn
BLK nnnnnnn
is the size of the virtual disk in storage in 512-byte blocks. The maximum size is
4194296 blocks.
1. A virtual disk in storage is allocated from system storage, not mapped to a real
DASD. Therefore, defining a virtual disk in storage does not require having a
real FBA DASD in your system configuration.
2. A virtual disk in storage must be formatted before it can be used. Using ICKDSF
is the preferred method for formatting the virtual disk in storage if it is to be
used as a system disk by a guest (such as VSE) or a second-level CP. The
CMS command FORMAT should be used to format the virtual disk in storage if
it is to be used as a CMS disk.
3. Virtual disks in storage are allocated in 8-block pages. Therefore, the size of the
virtual disk in storage that is created may be rounded up to the nearest page.
You can use all of the blocks in the created virtual disk in storage.
4. If you define a virtual disk in storage as virtual device number 192, the following
special rules apply when you IPL CMS:
v If 192 is unformatted, CMS formats it and accesses it as file mode D.
v If 192 is CP-formatted, CMS reformats it for CMS use and accesses it as file
mode D.
v If 192 is CMS-formatted and accessed as a file mode other than D, CMS
reaccesses it as file mode D.
When CMS accesses a 192 minidisk as file mode D, any minidisk or SFS
directory already accessed as D is released.
5. For more information, see “Usage Notes” on page 113.
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