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

To see the real spooled output, specify a CP CLOSE command for that
device to the real CP system. Also, note that double separators occur.
For instance, the separator page on virtual printed output includes four pages (two for the virtual CP system and two more pages for the
separator of the virtual machine on which the virtual CP system is
running). The extra set of separator pages can be avoided by usinq the START 60mmand with the NOSEP option. -
Because the virtual machine operation at
there is nc easy way of describing how to do
requires careful study and analysis. At all
awareness of at what level of virtual machine
function the user is trying to perform.
this level is complex,
all the functions. It
times it requires an
is operating and what Example -- Running VM/370 Under VM/370 The following sample terminal session illustrates how to run a virtual CP system in a virtual machine environment. It is annotated to point out
some of the mere pertinent considerations. r-------------------------------------------, vm/370 online Ijh359 qsyosu I I logon v145r I ENTER PASSWORD: I I LOGMSG - 17:20: 14 EDT THURSDAY mm/dd/yy I * RUNNING SYS061--IPL 7 I * QUERY LOG FOR RESTRICTIONS I LOGON AT 18:38:06 EDT THURSDAY mm/dd/yy I L-- _____________________________________ This segment shows a normal logon procedure for a user identified as V145R. This userid is defined in the real CP directory with sufficient
optiens and configurations to run VM/370 in a virtual machine
environment.
query virtual STORAGE = 00512K RDR OOC CLS A PUN OOD CLS A COpy 01 PRT OOE CLS A COpy 01 CONS 01P ON DEV 051 DASD 190 2314 CMS370 R/O 056 CYL DASD 19A 2314 CMS190 RIO 055 CYL DASD 19E 2314 CMS190 RIO 026 CYL DASD 290 2314 PIDSK3 RIO 045 CYL DASD 330 3330 PIDSK4 R/W 020 CYL L-- __________________ __
After logon, issuing the QUERY VIRTUAL command permits a user to
verify the virtual machine configuration. The response indicates: • The storage size is 512K bytes. • SeIDe unit record devices have been defined.
56 IBM VM/370 Operating Systems in a Virtual Machine