DEDICATED CHANNELS A user can have an entire channel with all its devices dedicated to his virtual machine. CD does not translate device addresses since the
virtual addresses must be the same as the real device addresses.
contention for use of the channel is minimized, since all of the channel resources are dedicated to a single virtual machine. The ATTACH CHANNEL
command is a class B command and is not usually available to the general
user. you can send a message to the system resource operator: msq operator pIs attach channel 2 to smith
If the channel is available, the operator issues:
attach channel 2 to smith
and the command has been successfully completed, you are notified by the
response:
CHANNEL 2 ATTACHED When a deiicated channel path is no lonqer required for virtual machine 1/0 operations, you can issue the command: detach channel 2 After the channel is detached, the following message is sent to you and
the primary system operator:
CHANNEL 2 DETACHED userid Controlling the Virtual Machine VM/370 provides several commands with which you can load an operating
system into your virtual machine, simulate hardware interruptions to your virtual machine, enter CP commands while in a virtual machine envirlnment, ani reconfigure your virtual machine dynamically during a
terminal session. LOADING AN OPFRATING SYSTEM the completion of the LOGON procedure, you have a virtual machine of
a predetermined configuration at your disposal. As with a real machine,
its use is limited without an operating system. An operating system can
be loaded via the IPL command or automatically at logon time if an IPL control statement is included in your virtual machine's directory entry.
When a virtual machine runs the same operating system with very few
exceptions, it .ay be expedient to use automatic loading. If the VM/370 directory entries for your userid include an IPL control statement with
the name or the virtual address of a specific system to be loaded, that
system is automatically loaded when you log on to VM/370 unless you
issue the LOGON command as:
loqon userid noip1
in which case, the automatic loading does not take place and you can IPL any supported system that is available.
22 VM/37Q CP Command Reference for General Users

A flexible approach is loading an operating system via the 1PL command. you have a choice. You can 1Pt by device address or by
system nane. If you IPt by the virtual address of the device containing
the operatinq system, you can also clear virtual storage to binary zeros before loajing the system:
ipl 190 ::lear This can be useful if your operating system does not
automatically clear storage when it is loaded. You can stop the IPt procedure at a point just before the initial PSi is loaled by issuing the IPt command with the STOP operand:
ipl 190 stop
At this point, you can issue CP commands to display or alter data in your - I. _, _ I""" 11:..a.\".,..L:: u::::> • beqin ..:I. ,",VIUWa.U u. You can loa5 your operating system by name provided that the name
refers to a system that has been previously saved by your installation's
system programmer. As an example:
ipl 10svs If do load by name, the options to clear storage or to stop before lOlling the initial PSW are not availablee Whether you TO! by device address or by name, you can pass up to 64 bytes lata (including embedded and trailing blanks) to your operating
system the IPt command. The data is entered following the keyword PARM: io1 10svs parm this data will be passed VM/370 loajs the qeneral registers, starting with register zero with
the contents of the command line beginning with the first nonblank
character after the keyword PARM and ending with the last character or
blank Embedded and trailing blanks are passed. For the previous example, the qeneral reqisters contain the followinq: G?R 0 THIS OAT A WI LL B GPR 4 E PA SSEO xxxx xxxx GPR 8 xxxx xxxx xxxx xxxx G1?R 12 xxxx xxxx xxxx xxxx
where x x ••• lenotes no change to previous contents.
If VOU hld entered three blank characters following the word "passed"
in the command line, the registers would contain: r;PR 0 GPR 4 GOR 8 G1?R 12 TQIS E PA xxxx
xxxx
OAT SSEO xxxx
xxxx
A WI x
xxxx
xxxx
Lt B
xxxx
xxxx
xxxx
For further information on the PARM operand, refer to the "Usage Notes"
discussion of the IPL command in Section 5.
Section 3. CP Command Usage 23