<s>
Single	O
Virtual	O
Storage	O
(	O
SVS	O
)	O
refers	O
to	O
Release	O
1	O
of	O
Operating	O
System/Virtual	O
Storage	O
2	O
(	O
OS/VS2	B-Application
)	O
;	O
it	O
is	O
the	O
successor	O
system	O
to	O
the	O
MVT	O
option	O
of	O
Operating	B-Application
System/360	I-Application
.	O
</s>
<s>
OS/VS2	B-Application
(	O
SVS	O
)	O
was	O
a	O
stopgap	O
measure	O
pending	O
the	O
availability	O
of	O
MVS	B-Application
,	O
although	O
IBM	O
provided	O
support	O
and	O
enhancements	O
to	O
SVS	O
long	O
after	O
shipping	O
MVS	B-Application
.	O
</s>
<s>
SVS	O
provides	O
a	O
single	O
16MiB	O
address	B-General_Concept
space	I-General_Concept
which	O
is	O
shared	O
by	O
all	O
tasks	O
in	O
the	O
system	O
,	O
regardless	O
of	O
the	O
size	O
of	O
physical	O
memory	O
.	O
</s>
<s>
OS/360	B-Application
used	O
the	O
Interval	O
Timer	O
feature	O
for	O
providing	O
time	O
of	O
day	O
and	O
for	O
triggering	O
time-dependent	O
events	O
.	O
</s>
<s>
The	O
support	O
for	O
S/370	B-Device
made	O
limited	O
use	O
of	O
new	O
timing	O
facilities	O
,	O
but	O
retained	O
a	O
dependency	O
on	O
the	O
Interval	O
Timer	O
.	O
</s>
<s>
OS/360	B-Application
loads	O
error	O
recovery	O
and	O
transient	O
SVC	B-Operating_System
routines	O
from	O
SYS1.SVCLIB	O
into	O
small	O
transient	O
areas	O
.	O
</s>
<s>
In	O
the	O
wake	O
of	O
the	O
Applied	B-Operating_System
Data	I-Operating_System
Research	I-Operating_System
lawsuit	O
IBM	O
decided	O
to	O
develop	O
chargeable	O
versions	O
of	O
several	O
applications	O
,	O
mostly	O
language	O
processors	O
,	O
although	O
it	O
's	O
not	O
clear	O
whether	O
the	O
lawsuit	O
was	O
actually	O
the	O
deciding	O
factor	O
.	O
</s>
<s>
As	O
a	O
result	O
,	O
SVS	O
does	O
not	O
include	O
a	O
sort/merge	B-Application
program	I-Application
or	O
any	O
language	O
processor	O
other	O
than	O
the	O
new	O
Assembler	O
(	O
XF	O
)	O
(	O
replacing	O
Assembler	O
(	O
F	O
)	O
)	O
which	O
is	O
required	O
for	O
the	O
system	B-Application
generation	I-Application
process	O
.	O
</s>
<s>
In	O
MVS	B-Application
IBM	O
enhanced	O
the	O
facility	O
to	O
allow	O
the	O
installation	O
to	O
designate	O
additional	O
data	O
sets	O
as	O
authorized	O
.	O
</s>
<s>
OS/360	B-Application
has	O
a	O
facility	O
called	O
Direct	O
SYSOUT	O
(	O
DSO	O
)	O
whereby	O
specific	O
output	O
classes	O
can	O
be	O
diverted	O
to	O
data	O
sets	O
on	O
tape	O
instead	O
of	O
normal	O
SPOOL	B-Device
datasets	O
.	O
</s>
<s>
As	O
DASD	B-Application
prices	O
dropped	O
,	O
the	O
facility	O
dropped	O
from	O
use	O
,	O
and	O
SVS	O
does	O
not	O
provide	O
it	O
.	O
</s>
<s>
OS/360	B-Application
provides	O
limited	O
interactive	O
facilities	O
in	O
Conversational	O
Remote	O
Job	O
Entry	O
(	O
CRJE	O
)	O
,	O
Graphic	O
Job	O
Processing	O
(	O
GJP	O
)	O
,	O
Interactive	O
Terminal	O
Facility	O
(	O
ITF	O
)	O
and	O
Satellite	O
Graphic	O
Job	O
Processing	O
(	O
SGJP	O
)	O
prior	O
to	O
the	O
Time	B-Application
Sharing	I-Application
Option	I-Application
(	O
TSO	O
)	O
,	O
but	O
IBM	O
did	O
not	O
carry	O
those	O
forward	O
to	O
SVS	O
.	O
</s>
<s>
TSO	O
continues	O
to	O
provide	O
equivalent	O
facilities	O
,	O
except	O
that	O
it	O
does	O
not	O
support	O
use	O
of	O
a	O
2250	B-Device
as	O
a	O
terminal	O
.	O
</s>
<s>
Use	O
of	O
2250	B-Device
from	O
a	O
batch	O
job	O
using	O
Graphics	O
Access	O
Method	O
(	O
GAM	O
)	O
and	O
Graphics	O
Subroutine	O
Package	O
(	O
GSP	O
)	O
remains	O
supported	O
.	O
</s>
<s>
OS/360	B-Application
includes	O
a	O
batch	O
debugging	O
facility	O
named	O
TESTRAN	O
;	O
it	O
is	O
clumsier	O
than	O
the	O
equivalent	O
facility	O
in	O
IBSYS/IBJOB	B-Operating_System
,	O
and	O
was	O
not	O
used	O
much	O
.	O
</s>
<s>
It	O
remained	O
available	O
until	O
Selectable	O
Unit	O
64	O
and	O
MVS/System	O
Extensions	O
Release	O
2	O
.	O
</s>
<s>
The	O
storage	O
key	O
facility	O
of	O
System/360	B-Application
and	O
System/370	B-Device
keeps	O
track	O
of	O
when	O
a	O
page	O
frame	O
has	O
been	O
modified	O
.	O
</s>
<s>
This	O
replaces	O
the	O
special	O
handling	O
of	O
refreshable	O
transient	O
SVC	B-Operating_System
routines	O
in	O
OS/360	B-Application
.	O
</s>
<s>
In	O
OS/360	B-Application
load	O
modules	O
can	O
be	O
permanently	O
loaded	O
at	O
Initial	O
Program	O
Load	O
(	O
IPL	O
)	O
time	O
into	O
an	O
area	O
of	O
real	O
storage	O
known	O
as	O
the	O
Link	O
Pack	O
Area	O
(	O
LPA	O
)	O
.	O
</s>
<s>
OS/360	B-Application
has	O
support	O
for	O
a	O
multiprocessor	O
version	O
of	O
the	O
360/65	O
.	O
</s>
<s>
SVS	O
provide	O
no	O
equivalent	O
support	O
;	O
customers	O
wanting	O
to	O
run	O
a	O
multiprocessor	O
System/370	B-Device
have	O
to	O
use	O
MVS	B-Application
.	O
</s>
<s>
OS/360	B-Application
introduced	O
Telecommunications	B-Application
Access	I-Application
Method	I-Application
(	O
TCAM	O
)	O
as	O
the	O
successor	O
to	O
Queued	B-Application
Telecommunications	I-Application
Access	I-Application
Method	I-Application
(	O
QTAM	B-Application
)	O
.	O
</s>
<s>
SVS	O
does	O
not	O
include	O
QTAM	B-Application
.	O
</s>
<s>
Because	O
of	O
the	O
larger	O
(	O
16	O
MiB	O
)	O
address	B-General_Concept
space	I-General_Concept
that	O
SVS	O
provides	O
,	O
there	O
is	O
less	O
external	O
fragmentation	O
than	O
in	O
MVT	O
,	O
and	O
Rollin/Rollout	O
would	O
provide	O
less	O
of	O
a	O
benefit	O
.	O
</s>
<s>
In	O
OS/360	B-Application
,	O
transient	O
SVC	B-Operating_System
routines	O
are	O
loaded	O
into	O
1	O
KiB	O
areas	O
known	O
as	O
SVC	B-Operating_System
Transient	O
Areas	O
,	O
and	O
a	O
considerable	O
amount	O
of	O
code	O
is	O
required	O
to	O
manage	O
them	O
.	O
</s>
<s>
In	O
SVS	O
,	O
all	O
SVC	B-Operating_System
routines	O
are	O
preloaded	O
into	O
virtual	O
storage	O
and	O
there	O
are	O
no	O
SVC	B-Operating_System
Transient	O
Areas	O
.	O
</s>
<s>
While	O
SVS	O
retains	O
the	O
SPOOL	B-Device
support	O
of	O
OS/360	B-Application
,	O
most	O
shops	O
used	O
ASP	O
or	O
HASP	O
,	O
the	O
precursors	O
of	O
JES3	O
and	O
JES2	O
,	O
respectively	O
.	O
</s>
<s>
SVS	O
has	O
16MiB	O
of	O
addressable	O
storage	O
in	O
a	O
single	O
address	B-General_Concept
space	I-General_Concept
,	O
regardless	O
of	O
the	O
size	O
of	O
physical	O
memory	O
.	O
</s>
<s>
The	O
nucleus	B-Operating_System
and	O
the	O
FLPA	O
are	O
Virtual	O
=	O
Real	O
(	O
V=	O
R	O
)	O
,	O
meaning	O
that	O
each	O
virtual	O
address	O
in	O
that	O
area	O
is	O
mapped	O
to	O
the	O
corresponding	O
physical	O
address	O
.	O
</s>
<s>
I/O	O
channels	O
on	O
S/370	B-Device
(	O
and	O
successors	O
)	O
do	O
not	O
have	O
the	O
ability	O
to	O
do	O
address	O
translation	O
.	O
</s>
<s>
SVS	O
provides	O
a	O
CCW	O
translation	O
service	O
as	O
part	O
of	O
the	O
Execute	B-Application
Channel	I-Application
Program	I-Application
(	O
EXCP	B-Application
)	O
SVC	B-Operating_System
.	O
</s>
<s>
EXCP	B-Application
will	O
do	O
any	O
necessary	O
page	O
fixing	O
,	O
allocate	O
storage	O
for	O
IDA	O
lists	O
,	O
translate	O
virtual	O
addresses	O
to	O
real	O
,	O
put	O
the	O
translated	O
addresses	O
into	O
the	O
appropriate	O
IDA	O
words	O
and	O
put	O
the	O
real	O
addresses	O
of	O
the	O
IDA	O
lists	O
into	O
the	O
translated	O
CCW	O
's	O
.	O
</s>
<s>
When	O
an	O
I/O	O
completes	O
,	O
EXCP	B-Application
reverses	O
the	O
process	O
,	O
freeing	O
storage	O
and	O
translating	O
status	O
back	O
into	O
virtual	O
.	O
</s>
<s>
In	O
addition	O
,	O
SVS	O
provides	O
the	O
Execute	B-Application
Channel	I-Application
Program	I-Application
in	I-Application
Real	I-Application
Storage	I-Application
(	O
EXCVR	B-Application
)	O
SVC	B-Operating_System
for	O
privileged	O
applications	O
that	O
do	O
their	O
own	O
paged	O
fixing	O
and	O
build	O
their	O
own	O
IDA	O
lists	O
.	O
</s>
