To tell iM/370 about the existence of these consoles, either use
directory statements or issue CP commands. The way a user specifies the
second console depends upon whether: • The user always wants to use a specific device at a specific IIC address.
--or-- • The user wants flexibility in selecting which device or terminal is
to be used. !§Su!E1ion: An OS/VS virtual machine is to run its 3158 display console
at address 01F in display operator console mode. Also, the virtual machine is to operate a local 3270 terminal at address 1B8.
Generate OS/VS with at least two consoles: 01F as the primary
console, and 009 as the secondary console. Specify the secondary console by directory statement. Code it: CONSOLE 009 3210 using the i8/370 CONSOLE Specify the OS/iS primary console either by having a DEDICATE statement in the VM/370 directory or by using the CP ATTACH command after logon. Either specification allows OS/VS to use
the 3158 console in display operator console If the DEDICATE statement is used, then code it: DEDICATE 01F 01F If the ATTACH command is used, then, after logon, send a
message to the VM/370 operator that requests the following ATTACH command to be issued:
msg op attach 01f to userid as 01f To use any attached 3270 display terminal as the OS/VS primary
ccnsole in display operator console mode, either have a SPECIAL statement in the virtual machine's V8/370 directory entry or issue the CP DEFINE cOlllla nd af te r log on to VM/370. If the SPECIAL statement is used, it appears as follows: SPECIAL 01P 3270 If the SPECIAL statement is not used, assume that a local 3270 line
has been enabled by the VM/370 operator .• Then, issue the following
DEFINE command:
define graf 01f 3270 Section 1. General Considerations 15

In either situation, after a user logs onto VM/370 (by using the
device specified in the CONSOLE statement) and loads the OS/VS system into the virtual machine, a user must issue the CP DIAL command at the
lecal 3270 that is to be used in display mode. This action logically
cennects that 3270 and its real I/O address of lB8 to the operating
system. To drop the dialed connection, a user must issue the CP RESET command.
Note: A remote 3270 cannot be used in this manner because the DIAL command does not support remote 3270 terminals.
If the second console is a remote terminal such as a 2741 or 3767
cennected by either a 2702 or a 3704/3705 in 2702 emulation mode, the SPECIAL state.ent would appear as follows: SPECIAL 01F 2702 IBM The DEFINE command would be:
define line as 01f ibm VIRTUAL MACHINE I/O MANAGEMENT
A real disk device and a real or emulated 270% transmission control unit (TCU) can be shared among multiple virtual machines. Virtual disk
device sharing is specified in the VM/370 directory entry or by a user command. A specific virtual machine may be assigned read-only or
read/write access to a shared disk device. To gain access to the shared
virtual device, a user must supply the appropriate password. To ensure
device integrity, VM/370 checks each virtual machine I/O operation
against the parameters in the virtual machine configuration.
The virtual machine operating system is responsible for the operation
of all virtual devices associated with it. These virtual devices may be
defined in the VM/370 directory entry of the virtual machine, or they may be attached dynamically to (or detached from) the virtual machine's
configuraticn for the duration of the terminal session. Virtual devices may be in one of these three states or conditions: • -- when mapped to a fully equivalent real device • Shared -- when mapped to a minidisk or when specified as a shared vIrtual disk device • -- when VM/370 places the device output on intermediate
direct access storage
For example: In a real machine when running under control of the
operating system, the problem program requests the system to issue a SIC instruction to a specific device. The operating system normally
initiates the I/O operation and handles any device error recovery. In a
virtual machine, the operating system performs the same functions, but
the device address specified and the storage locations referenced are
both virtual. VM/370 has the responsibility for translating the virtual
specifications to real. When I/O interruptions occur, VM/370 reflects them to the virtual machine for its interpretation and processing. When I/O errors occur. VM/370 records the error, but it does not initiate error recovery
operations. The operating system must handle error recovery_ 16 IBM VM/370 operating Systems in a Virtual Machine