CPASSIST {ON } OFF sets CP assist to the active or the nonactive state. If CP
assist is active, functions normally executed by various
sections of CP routines are executed by processor hardware
logic. This function made active on VM/370 initialization, a
part of VM/370 Extended Control-Program Support (VM/370 ECPS), is available on System/370 models and 148.
Expanded virtual machine assist, another part of V8/370 ECPS, is also controlled by the SET CPASSIST ON and OFF operands.
Expanded virtual machine assist, an extension of function
provided by virtual machine assist, is set to the active state
upon '"/370 system initialization. Thereafter, to enable this
function, both SET CPASSIST ON and SET SASSIST ON commands must be invoked. To set expanded virtual machine assist to
the inactive state, use either SET CPASSIST OFF or SET SASSIST OFF. r , FAVORED userid Ixx I 10FFI L .J
sets the favored execution performance option for the
specified user (userid). The FAVORED function with percentage
(xx) specified can be in effect for only one virtual machine at any time. If xx (percentage values from 1 to 99 are valid)
is specified, VM/370 attempts to provide up to the specified
percentage of processor time to that virtual machine, provided
that virtual machine can fully utilize the processor time. At regular time intervals, the VM/310 dispatcher checks the
processor time used by the particular virtual machine; if the
percentage has been exceeded, the virtual machine is given his normal priority usage for the remainder of the interval. If
the percentage is low, the virtual machine is assigned highest
priority for the remainder of the interval. If OFF is
specified, the specified virtual machine is removed frem FAVORED status. If neither xx nor OFF is specified, the
virtual machine designated is always dispatchable; that is,
any time it is ready to use processor time, it is .given preference over other usets with the same priority. Multiple users may be classified as favored if they have no percentage
assigned; however, only one user may be designated in a single SET command. r , JOURNAL {LOGOI} 101 ! LINK IOFFI L .J
sets the status of the LOGON and LINK journaling functions. RESERVE user id {xx } OFF the reserved page performance oFtion for the specified user (userid). This performance option can be applied to only
one virtual machine at any time. The specified virtual
machine uses only the specified number of page frames (xx) for
its exclusive use. If the number of page frames does not
equal the most active pages, the virtual machine will
experience performance degradation. The page frames are not
locked and the virtual machine can also use other available
page frames; however, no other virtual machine can use a
reserved page frame unless all other available page frames 140 V"/370 Operator's Guide
SASSIST have been exhausted. The maximum number of page frames reserved is limited by the size of the virtual machine. The OFF operand returns the reserved pages to the system. {
ON
} [[ PROC ]nn ] OFF controls whether virtual machine assist, a facility available
on most VK/370 supported System/370 processors, is activated
or deactivated for the entire system. In VK/370 attached
processor applications, virtual machine assist may be set
either ON or OFF for the desired processor by selecting the PROC nn operand. If PROC nn is not selected then SET SASSIST ON or OFF determines the setting of virtual machine assist for
both the main and the attached processor. The values of nn
are processor addresses (hexadecimal values 00 to 3F)
established when the System/370 is installed. If nn equates
to a value that is not the address of the main processor or
attached processor, an error message is issued. Virtual
machine assist increases the efficiency of CP processing of
certain instructions, privileged instructions, and interrupts
reflected to CPa SET SASSIST in conjunction with CPASSIST also controls whether
the VK/370 Extended Control-Program Support provided by System/370 Kodels 135-3, 138, 145-3, and the 148 is in an
active or inactive state. For details on how this is
accomplished, refer to the CPASSIST operand previously
described. VK/370 Extended Control-Program support simulates
the CP processing ot additional privileged instructions and
extends the level of handling of other privileged instructions
not covered by virtual machine assist. SET SASSIST ON or OFF also controls whether the virtual interval timer assist
function of ECPS, a hardware updating' facility for the
interval timers of virtual machines, (virtual location X'50') is available to users. Use of this timer hardware update
facility by the virtual machine is controlled by the class G
command SET ASSIST TKR or SET ASSIST 10TKR; for details, see
the !!L37Q Upon system initialization, the default value SET SASSIST is ON for VK/370 processors except the system/370 Kodel 155 II
and the 165 II .. For details on the extent of virtual machine assist and the VK/370 Extended Control-program Support, refer to the PRIORITY userid nn
sets the priority of the specified user (userid) to the
desired value This value affects the user's dispatching
priority in relation to other users in the system. The
priority nn value is one of the factors considered in VK/370's dispatching algorithm. Generally, the lover the value of nn,
the aore favorable the user's position in relation to other
users in VK/370's dispatch queues.
Section 3. CP Commands 141
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