You can assign multiple virtual machines the favored execution option only one virtual machine at a time can be assigned a specified favored
percentage value.
set favored operatns 75
set favored payroll
set favored revenue
set favored hot jobs VIRTUAL=REAL OPTION The virtual=real option permanently relocates the CP nucleus (except for
real page 0) to provide space in real lower storage to contain the
largest virtual=real machine. For the virtual machine, each page froa
page 1 to its last or page is in its true real storage location; only its page zero is relocated. The virtual machine still runs in
relocate mode, but because each virtual page frame address is the same as the real page frame address, the virtual machine requires no CCW translation for the virtual machine. Because no CCW translation is DO check is made of the I/O data addresses. The virtual
machine must ensure that no I/O data transfer occurs into real page zero
or beyond the upper boundary of the virtual aachine's storage. Failure
to observe these limits can cause daaage to the VM/370 systea or to
other virtual machines. Initial program loading of a named or shared systea is not allowed in
the virtual=real machine; the hexadeciaal device address must be used. Several aspects of the operation of the virtual=real option can
affec't overall system operation:
1. The area of contiguous storage built for the virtual=real machine must be large enough to contain the entire addressing space of the
largest virtual=real .achine. 2. Only virtual machines with the virtual=real option can use the real
storage reserved for virtual=real machines. Only one virtual=real virtual machine can run at a time. The storage is not available
for other users, nor for VM/370 use, unless the virtual=real
machine is not logged on and you issue an UNLOCK command with the VIRT=REAL option. When you this command, all page frames previously reserved for the virtual=real machine are permanently
relinquished to the available-page pool. Once these virtual=real
page frames are available to the page pool, no virtual=real machine can run until you load VM/370 again (via IPt). For this reason, it
is suggested that the virtual=real aachine should machine with
high availability and heavy workload deaandso It possible
to relinquish only soae of the virtual=real page frames (if, for
exaaple, a smaller virtual=real aachine is to be run). All
virtual=real page fraaes are locked until all are released to the
pool. Section 2. Initiating VM/370 Operation 29

3. The virtual=real machine operates in its allocated storage area with normal CCi translation in effect until the virtual machine
operator issues the CP command: SET NOTRINS ON this ti.e, all subsequent operations occur fro. the virtual CCWs in the virtual=real machine without translation. with BOTRINS on, the virtual machine must not perform I/O operations into page
zero or beyond its addressable limit. Is mentioned previously,
violation of this requirement can cause damage to the V8/370 system or to other virtual machines.
4. If the virtual=real machine performs a reset or IPL, the normal CCW translation routine regains control until the virtual machine
operator again issues the SET NOTRINS ON command. Only the
virtual=real machine operator can use the command. In operator message occurs if the virtual machine enters normal translation
mode.
The virtual=real option is used with programs or operating systems
that dynamically modify channel programs, or that wish to avoid CP
virtual channel program translation and paging degradation. If
virtual=real operation is desired, it must be specified at V8/370 system generation time. iirtual=real assigns the same real storage locations
to the virtual machine that exist on the real machine (except for page
zero, which is relocated). Por example, in Pigure 2, if a DOS system needs 160K bytes to run
virtual=real, CP puts all but the first 4096 bytes of the program at the
real storage address locations. Page 0 of the DOS supervisor is the
only part of the DOS virtual machine that can be relocated, and it
follows the last real page frame of the DOS machine. Pigure 2 also
shows that the major portion of the CP nucleus is permanently relocated
into upper storage (except for page zero) whether the virtual=real system is operating or not. The real page frame zero remains under
control of i8/370. CP dedicates 160K nonpageable bytes to the DOS machine. However, when the user no longer needs the virtual=real machine performance option and he logs off, the assigned virtual=real storage
can be reallocated as available pageable storage for use by other
virtual machines (assuming that no other users with the VIRT=REIL directory have need of the area). The reallocation of virtual=real
storage as usable and available storage for other virtual machines is
controlled by the UNLOCK command and the VIRT=REAL operand. Once the
pages are released, no virtual=real machine can be run unless V8/370 itself is reloaded. If more than one virtual machine needs the
capabilities of running virtual=real (at different times), V8/370 system generation parameters must specify the largest virtual machine that is
to run in the virtual=real environment. I more practical approach may be to generate a different version of V8/370 for each virtual=real machine, if the storage sizes are substantially different. 30 YM/370 Operatoris Guide