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

ACCESSING DEVICES Once a user IPLs the virtual machine, the devices that were not
accessible to that machine at IPL time are considered offline. However,
the user can attach more devices to this machine and have them placed
online as required. For example: Tape drives can be attached by the
real machine oFerator to the virtual machine configuration at the
required address that matches the configuration of the virtual CP system. The same procedure can be used for teleprocessing lines, unit
record equipment, or other devices. Most testing can be done by initializing and running
the operator's virtual machine without enabling any
teleprocessing lines.
tests from
virtual
Teleprocessing lines and spool unit record devices can be created by using the CP DEFINE command. Before the virtual CP operator can attach
these lines er devices to a virtual machine user, they must first be placed online at the virtual machine level. Once online, they can be
attached and used by virtual machines in the virtual CP system.
(Teleprocessing lines can be attached directly to the virtual CP system
fer testing in that environment without using the CP DIAL command.)
It is possible to use virtual disks in the virtual CP system; their setup is complex and requires careful coordination with the real
directory of the real system. For example: If a virtual disk is moved
and the real directory of the real system is changed but the virtual
directory is not changed, serious operating errors can occur; therefore,
de net use virtual disks in the virtual CP system unless they are
required fer a specific test.
Note: When a virtual machine is linked to virtual disks before the user IPLs a system to run in the virtual machine, the virtual disks appear to
the virtual system as disks with a zero cylinder relocation factor; that
is, for CMS te access them at the virtual CP level, attach the disks at
the CP level. Then the user can access them as though they were
dedicated disks. Otherwise, accesses beyond this disk cause the real CP system to present I/O errors in the form of seek checks to the virtual CP system, which, in turn, reflects the errors to the virtual operating
system. SPOOLING CONSIDERATIONS If the virtual machine performs any spooling operations, the virtual CP system is also sFooling unless it has dedicated unit record devices.
This double speoling operation is not a problem; however, certain operational Feculiarities exist. For example: ihen the virtual system specifies that a printer is producing output, the output is in fact
being sFecled. However, the user cannot easily determine when this spooling operation is complete. One way to make this determination is
tc specify a CP DRAIN command on the particular output device. When the
virtual CP system reports that the device is drained, the output has
indeed stopped.
Section 2. VM/370 in a Virtual Machine 55