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

April 1, 1981
To create the virtual directory for the virtual system residence
volume, run CMS in the same virtual machine. First, set up a CMS file
on one of the virtual disks. Second, have the virtual VM/310 user link
to the CMS file with the desired filename and the filetype of DIRECT.
The DIRECT proqram that is given control under CMS uses this file to
create the virtual system's directory. Note: The DIRECT file must contain sufficient directory entries to test VM/370 in a virtual machine environment. VirtuallPL and Operation Once a user has verified (by using a QUERY VIRTUAL command) that the
virtual machine configuration matches the one that he wishes to test, he
can perform a virtual IPL of the virtual disk containing the CP nucleus.
(In the example used at the beginning of this section, it is disk 330.) Because a terminal is handled like a simulated virtual console, (this
example uses a 2741 terminal), each exclamation point (!) appearing in
the sample terminal output indicates that the attention key has been
pressed. The operation of the attention (ATTN) key on the terminal
remains the same as it would have been if running any other system, but
the opec at ion of the virtual console is as though the device were an
online console (3215) and not a 2741. Note: Attention handling varies with the type of terminal used. Refer
to the User's for a list of the terminals
supported by VM/370. Proceed through the virtual machine IPL in the normal fashion,
respondinq where required. Because the virtual VM/370 user cannot set
the time-of-day clock, always reply "no" to the change time-of-day clock
question. Under most circumstances, it is advisable to perform a cold
start unless some specific function requiring a warm start is to be
tested. When the test system has read/write access to a eMS minidisk,
it can use the IPCS component of VM/370 to process any dumps taken of
the virtual CP system. By using IPCS in the test system, an
installation can standardize its VM/370 problem reporting and tracking
process.
To place dumps of the virtual CP system in the test system's virtual
reader:
1. Specify the test system's userid in the SYSDUMP operand of the SYSOPR system generation macro instruction.
2. Initialize the virtual CP system by assuming the SET DUMP AUTO CP command (class B) by default. The test system's userid in the SYSDUMP operand should be OPERATOR, rather than the default of OPERATNS. OPERATOR helps the user
to reaiily identify his dumps. It also makes the dump immediately
available to the OPERATOR virtual machine user for IPCS processing. Once the user IPLs the virtual machine and logs on the operator's
virtual machine, he can operate virtual operating systems under this
userid or enable virtual teleprocessing lines. Enabling these lines
allows other users to dial into this system, log on to VM/370 in a
virtual machine, and perform whatever actions they require.
54 IBM VM/370 Operatinq systems in a Virtual Machine