April 1, 1981
52.2 IBM VM/170 Operatinq Systems 1n a Virtual Machine

Page of GC20-1821-3 As Updated April 1, 1981 by TNt GN25-0840 CP DISKS FOR THE VIRTUAL MACHINE Before VM/370 in a virtual machine can use the CP disks for the virtual
system residence, paging, and spooling volumes, an installation must
first format and allocate space for these disks.
To format the system residence, paging, and spooling volumes, use the CP format/allocate program. Although this program can run in a virtual
machine, it cannot run under CMS. To run the format program, make it
available to the virtual machine by reading it into the virtual
machine's spool card reader. Then, IPL it from that reader. Because a
virtual disk is being formatted, the cylinder specification should
reflect the size of the virtual disk being used. For example: In the
sample directory entry for TESTSYS (described earlier in this section),
the MDISK statement for the virtual disk at real address 330 defines
only 15 cylinders for the device; thus, only 15 cylinders on the virtual
disk at real address 330 can be formatted.
When the virtual machine is going to use the same DMKSYS module that
the installation is using, the virtual disk label should match the label
in the installation-owned list. Thus, if an installation has two
volumes in the owned list (such as CPDSK1 and CPDSK3), then those volume
labels must match the minidisk labels used by the virtual machine.
After formatting the volumes, allocate space on them to hold: • A virtual directory • Nucleus cylinders • Warm start cylinders • Error recording cylinders Q Temporary space for paging and spooling
If the space is inaccessible to the virtual
beyond the size of the virtual disk), it must
space. Otherwise, the virtual system attempts
beyond the size of the virtual disk, resulting
reflecting seek checks to the virtual system. VM/370 system (that is,
be assigned as permanent to access temporary space
in the real VM/370 system
When allocating permanent space, organize the cylinders to hold the
directory, CP 'nucleus, error recording area, and the warm start cylinders. Also, organize the cylinders to begin with the first
cylinder available on the disk. If the real system residence volume
uses this same organization, the disk you use for your virtual system
residence volume can use the same DMKSYS and DMKRIO For example: If the real configuration specifies permanent space,
then the installation must generate a special DMKSYS module for the VM/370 system in a virtual machine. When operating in a virtual
machine, it is preferable that the same installation modules be used.
using the same modules ensures that the testing environment matches the
modules used in the real machine configuration. The only exception to
this rale is the directory that appears on the virtual disk. The directory on the virtual disk cannot be the same as the real system
directory because none of the labels and displacements for the user
disks match.
Section 2. VM/370 in a virtual Machine 53