protection applies, the protection key of the processor occupies bit
positions 8-11 of the
protection applies, the protection key associated with the
is used as the comparand. The protection key for an
specified in bit positions
recorded in bit positions
a result of the
To use fetch protection, a virtual machine must execute the
protected, with the fetch protect bit set on in the key.
1. Checks for a fetch protect violation in handling privileged and
key) when writing and recovering virtual machine pages from the
3. Checks fer a fetch protection violation on a write
spooling or console devices).
case for storage protection since the nucleus must be protected and
still shared among many
in the shared segment, user programs and disk-resident
with a different key than the nucleus code.
The system operator may assign the reserved page frames option to a
single virtual machine. This option, specified by the
the virtual machine.
real storage page frames for this virtual machine during its execution
until the' maximum number "reserved" is reached.
other virtual machines are not allocated from this reserved set, the
effect is that most of the active pages of the selected virtual machine
remain in real storage.
allocated directly from real storage at the time the virtual machine
logs on (if it has the
except page zero are allocated to the corresponding real storage
locations. In order to control the real computing system, real page
zero must be controlled by
be large enough to accommodate the
virtual machine, and the remaining pageable storage requirements of
The virtual=real option improves performance in the selected virtual
machine since it removes the need for
selected virtual machine. The virtual=real option is necessary whenever
programs that contain dynamically modified channel programs (excepting
modified channel programs, see
in "Part 1. Debugging with