Directory Program ISAM channels. If a virtual machine with the option
executes in basic control mode, the I/O masking for channels 6
and higher is simulated by the extended channel feature. If a
virtual machine with the EC"ODE option executes in extended
control mode, the I/O masking for all 16 channels is handled
via extended control register 2. This facility can also be
obtained by issuing the CP command SET EC"ODE ON. provides special channel command word translation routines
that permit as/pcP, "FT, and MVT ISA" programs (which
dynamically modify their CCis) to operate properly in a
virtual machine. This is required only for virtual machines
that use as/pcP, or MVT ISAM access methods or OS/VS ISA" when executing in a V=R partition under OS/VS. This option is
not needed for DOS, DOS/VS, or OS/VS ISAM when run only in a V=V partition of OS/VS. This facility can also be obtained by
issuing the CP command SET ISAM ON. VIRT=REAL is a performance option that allows the user to place his
virtual machine in lower storage. such that its virtual
storage addresses correspond to the real storage address
(except for its page zero, which is relocated). The real page ACCT SVCOFF zero is controlled by the CP nucleus. No CCi translation is
required. This option is required for a virtual machine to
successfully execute self-modifying channel programs other
than those generated by OS/VS TCAM (Level 5, generated or
invoked with the VM/370 option) or OS ISAM. VIRT=REAL can be
specified for any number of virtual machines but only one
virtual machine can use this facility at any given time. A
named or shared system cannot be loaded (via IPL) in a
virtual=real area. The device address must be specified in
the IPL command. To generate a VM/370 system with a
virtual=real machine, see "Specifying a Virtual=Real Machine" in the Part 1.
a user with the ACCT option in his directory can charge
another user for virtual machine resources. For example, a
user who sends a job to the CftS batch virtual machine can be
charged for the time that he uses in the batch machine. Note
that the ACCT option should be specified in the directory of
the CftSBATCH virtual machine so that user/job identifying
information will be printed on the forms separator that
separates spooled output files.
specifies that CP, instead of the virtual machine assist
feature or the V"/370 Extended Control - Program Support handles all SVC interrupts for this virtual machine. A user
whose directory entry contains this option can override it by
issuing SET ASSIST SVC. All SVC 76 interrupts are handled by CP whether or not
the SVCOFF option is specified. BftX specifies that all virtual machine I/O operations are to occur
as block multiplexer channel operations rather than selector
channel (the default) operations. In block multiplexer mode, the virtual channel is not busy until the initial 510 is
complete (selector mode operates similarly). Block
multiplexer allows the successful start of multiple SIOs to
different devices on the same channel. However, virtual I/O operations on channel 0 are processed as byte multiplexer
channel operations. Channels that have a channel-to-channel
adapter are restricted to selector channel operation. 204 IBft VM/370 Planning and System Generation Guide

The channel mode
channel zero can
CHANNEL command. CPUID bbbbbb
Directory Program setting for all channels
be changed by the use of
except virtual
the CP DEFINE
provides a unique processor identification (CPUID) to be
stored in response to the STIDP instruction. It is necessary
to associate a unique CPUID with each virtual machine that is
attached to an MSC port since solicited/unsolicited messages
are directed to the host system in the virtual environment by
means of the CPUID. There is no checking by VM/370 to ensure
that all virtual machines using the SET CPUID command have
specified unique processor serials. The hexadecimal field Ibbbbbb
i is the processor identification number. The
processor identification number (serial) is only a portion of
the complete CPUID. The CPUID identification stored in
response to a STIDP instruction is a string of 16 hexadecimal
digits shown as follows:
aabbbbbbccccdddd
aa is the version code; these X'FF' to identify that the
under VM/370. two digits are forced to
virtual machine is running
bbbbbb is up to 6 hexadecimal digits that indicate the
processor identification number; this field is set by
the directory OPTION statement values or modified by
the SET CPUID command.
cccc is the model number; this field contains a high order
o digit followed by the three digits of the model
number (0-9). This field defaults to the model number
of the real machine.
dddd is the machine check extended logout; this field is
forced to X'OOOO' since CP does not reflect machine
checks to the virtual machine.
If the CPUID was not specified by means of the SET CPUID command or the OPTION control statement, the CPUID stored as a
result of the STIDP instruction is the real CPUID with the
first two digits set to X'FF' and the last four digits set to X'OOOO' (present CPUID logic). A processor serial of more
than six digits on the SET CPUID command results in an error
message.
A processor identification number (serial) of less than six
hexadecimal digits results in zeros being padded to the left
of the number. A three-byte field in the VMBLOK (VMCPUID) contains the value set as a result of invoking this DIRECTORY option. AFFINITY nn
is 2 decimal digits between 00 and 63 that specify that
virtual machine execution is to be performed on a designated
processor (nn). This attribute is only applicable in the VM/370 attached processor environments. Any hexadecimal value
from 00 to 3F is a valid main or attached processor address;
however, the value selected must match the preset values
established for your installation's main and attached
processor when the system was installed. If the AFFINITY option is not selected, then the virtual machine is serviced Part 2. Defining Your VM/370 System 205