cation programs written for System/360 that satisfy
the conditions described in"Compatibility." Availability
Availability is the capability of a system to accept
and successfully process an individual job.System/370 machine facilities permit increased
availability by (1) allowing a larger number and a
broader range of jobs to be processed concurrently,
thus making the system more readily accessible to
any particular job, and (2) limiting the effect of an
error and identifying more precisely its cause, with
the result that the number of jobs affected by errors
is minimized and the correction of the errors is facili
tated.
Several design aspects make this possible.• A program is checked for the correctness of
instructions and data as the program is execut
ed, and program errors are indicated separately
from equipment errors. Such checking and re
porting assists in locating failures and isolating
effects.• The protection facility, in conjunction with dy
namic address translation, permits the protec
tion of the contents of main storage from de
struction or misuse caused by erroneous or
unauthorized storing or fetching by a program.
This provides increased security for the user,
thus permitting applications with different se
curity requirements to be processed concur
rently with other applications.• Dynamic address translation allows isolation of
one application from another, still permitting
them to share common resources. Also, it per
mits the implementation of virtual machines,
which may be used in the design and testing of
new versions of operating systems along with
the concurrent processing of application pro-
grams. Additionally, it provides for the concur
rent operation of incompatible operating sys
tems.• Multiprocessing permits better use of storage
and processing capabilities, more efficient
communication between CPUs, and duplica
tion of resources, thus aiding in the continua
tion of system operation in the event of ma
chine failures.• Monitoring, program-event recording, and the
high-resolution timing facilities permit the test
ing and debugging of programs without manual
intervention and with little effect on the con
current processing of other programs.• Emulation is performed under supervisory pro
gram control, thus making it possible to per
form emulation concurrently with other appli
cations.• On most models, error checking and correction
(ECC) in main storage, instruction retry, and
command retry provide for circumventing in
termittent equipment malfunctions, thus reduc
ing the number of equipment failures .• An enhanced machine-check handling mecha
nism providesmodel-independent fault isola
tion, which reduces the number of programs
impacted by uncorrected errors. Additionally,
it provides model-independent recording of
machine-status information. This leads to
greater machine-check handling compatibility
between models and improves the capability
for loading and running a program on a differ
ent model when a system failure occurs.• A small number of manual controls are required
for basic system operation, permitting most
operator-system interaction to take place via a
unit operating as anI/O device and thus reduc
ing the possibility of accidental operator errors.
IBMSystem/370 11
the conditions described in
Availability is the capability of a system to accept
and successfully process an individual job.
availability by (1) allowing a larger number and a
broader range of jobs to be processed concurrently,
thus making the system more readily accessible to
any particular job, and (2) limiting the effect of an
error and identifying more precisely its cause, with
the result that the number of jobs affected by errors
is minimized and the correction of the errors is facili
tated.
Several design aspects make this possible.
instructions and data as the program is execut
ed, and program errors are indicated separately
from equipment errors. Such checking and re
porting assists in locating failures and isolating
effects.
namic address translation, permits the protec
tion of the contents of main storage from de
struction or misuse caused by erroneous or
unauthorized storing or fetching by a program.
This provides increased security for the user,
thus permitting applications with different se
curity requirements to be processed concur
rently with other applications.
one application from another, still permitting
them to share common resources. Also, it per
mits the implementation of virtual machines,
which may be used in the design and testing of
new versions of operating systems along with
the concurrent processing of application pro-
grams. Additionally, it provides for the concur
rent operation of incompatible operating sys
tems.
and processing capabilities, more efficient
communication between CPUs, and duplica
tion of resources, thus aiding in the continua
tion of system operation in the event of ma
chine failures.
high-resolution timing facilities permit the test
ing and debugging of programs without manual
intervention and with little effect on the con
current processing of other programs.
gram control, thus making it possible to per
form emulation concurrently with other appli
cations.
(ECC) in main storage, instruction retry, and
command retry provide for circumventing in
termittent equipment malfunctions, thus reduc
ing the number of equipment failures .
nism provides
tion, which reduces the number of programs
impacted by uncorrected errors. Additionally,
it provides model-independent recording of
machine-status information. This leads to
greater machine-check handling compatibility
between models and improves the capability
for loading and running a program on a differ
ent model when a system failure occurs.
for basic system operation, permitting most
operator-system interaction to take place via a
unit operating as an
ing the possibility of accidental operator errors.
IBM