In most cases, the
among many virtual machines as minidisks and dedicated devices, and
balance between virtual machines. In
areas of each virtual machine.
By specifying a dedicated
function is bypassed for that virtual machine. A virtual machine
assigned a dedicated channel has that channel and all of its devices for
its own exclusive use.
specified in channel commands to real locations and performs any
necessary paging operations, but does not perform any device address
translations. The virtual device addresses on the dedicated channel
must match the real device addresses; thus, a minidisk cannot be used.
record device, is said to be dedicated. The real device is then
controlled completely by the virtual machine's operating system.
modest requirements for unit record input/output devices, such device
sharing is advantageous, and it is the standard mode of system
to spooling is exhausted, and the virtual unit record devices appear in
a not-ready status. The system operator may make additional spooling
space available by purging existing spool files or by assigning
additional direct access storage space to the spooling
printer of a virtual machine to the card reader of the same or another
virtual machine. Files transferred between virtual unit record devices
by the spooling routines are not physically punched or printed.
or to different operating systems executing at different times in the
same virtual machine.
Files may also be spooled to remote stations via the Remote
user and the real machine operator. These options include printing
multiple copies of a single spool file, backspacing any number of
printer pages, and defining spooling classes for the scheduling of real
output. Each output spool file has, associated with it, a 136-byte area
known as the spool file tag. The information contained in this area and
For example, whenever an output spool file is destined for transmission