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users (those with privilege classes other than G), using QUERY without the
keyword "VIRTUAL" displays information about the real machine. For
instance, QUERY VIRTUAL STORAGE displays the virtual storage size of
the virtual machine while QUERY STORAGE (class B and E) displays the
real machine storage size.
Related information
z/VM: CP Commands and Utilities Reference, SC24-6175
Overview of the CP spool file system
In the early days of computing, input to the computer came from punched cards
loaded into a card reader. You used a key punch to record your program on
punched cards, then loaded the cards into a card reader, which interpreted your
cards and loaded your program into the computer. Output from the program was
written to a printer. z/VM preserves this bit of computing history through virtual
reader, punch, and printer devices, also called unit record devices. Unit record
devices provide a handy way to send files from one virtual device to another, to
other virtual machines, or to real devices (such as real printers). For instance, you
can think of a file being sent from one virtual machine to another as the virtual
equivalent of taking a card stack from one computer and loading the stack onto
another computer's card reader.
Behind the manipulation of these files is a CP file system called the spool file
system. CP manages spool files on one or more DASD volumes that act as
temporary storage areas. A spool file is a collection of data along with device
control instructions for processing on a unit record device. Spooling is the
processing of files created by or intended for virtual readers, punches, and printers.
Through CP and CMS commands, you can send spool files from one virtual device
to another, from your virtual machine to another, and to real devices.
By convention, each virtual machine has a virtual reader at virtual device number
00C, a virtual punch at virtual device number 00D, and a virtual printer at virtual
device number 00E. Your virtual reader is like the in-box of an e-mail system,
except more than just e-mail can be placed there. Through your virtual punch, you
can place a copy of an entire operating system into the system spool, then use the
CP IPL command to load and run that operating system in your virtual machine.
"Installing Linux in a virtual machine" on page 77 shows you how to use this
z/VM facility.
Some important commands that operate on spool files are:
v SPOOL. Use the CP SPOOL command to set control options for one or more of
your virtual spool devices. A handy way to keep a log of your system activity is
to spool your console (SPOOL CONSOLE *, meaning send the console log to
yourself), which keeps all your console activity in a spool file. When you close
your console (SPOOL CONSOLE STOP CLOSE), your console log is sent to you.
v QUERY READER ALL. This CP command lets you view information about spool
files in your virtual reader.
v RDRLIST. This CMS command displays information about your reader files in a
full-screen interactive display.
v RECEIVE. This CMS command moves a file from your reader onto a minidisk.
v PUNCH. This CMS command punches (copies) a CMS file to your virtual
punch.
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Chapter 1. About z/VM
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