<s>
System	B-Application
Generation	I-Application
(	O
SysGen	O
)	O
is	O
a	O
two-stage	O
process	O
for	O
installing	O
or	O
updating	O
OS/360	B-Application
,	O
OS/VS1	B-Application
,	O
</s>
<s>
OS/VS2	B-Application
(	O
SVS	O
)	O
,	O
OS/VS2	B-Application
(	O
MVS	B-Application
)	O
and	O
chargeable	O
systems	O
derived	O
from	O
them	O
.	O
</s>
<s>
Also	O
,	O
some	O
of	O
the	O
details	O
have	O
changed	O
between	O
releases	O
of	O
OS/360	B-Application
and	O
many	O
details	O
do	O
not	O
carry	O
over	O
to	O
later	O
systems	O
.	O
</s>
<s>
There	O
are	O
several	O
reasons	O
that	O
IBM	O
provided	O
a	O
system	B-Application
generation	I-Application
process	O
rather	O
than	O
simply	O
providing	O
a	O
mechanism	O
to	O
restore	O
the	O
system	O
from	O
tape	O
to	O
disk	O
.	O
</s>
<s>
As	O
a	O
result	O
,	O
IBM	O
had	O
to	O
provide	O
a	O
mechanism	O
for	O
the	O
customer	O
to	O
define	O
the	O
I/O	O
configuration	O
to	O
OS/360	B-Application
.	O
</s>
<s>
Also	O
,	O
OS/360	B-Application
supported	O
several	O
different	O
options	O
;	O
IBM	O
needed	O
a	O
way	O
for	O
the	O
customer	O
to	O
select	O
the	O
code	O
appropriate	O
for	O
the	O
options	O
needed	O
at	O
a	O
particular	O
installation	O
.	O
</s>
<s>
Stage	O
1	O
is	O
the	O
compilation	O
of	O
a	O
sequence	O
of	O
assembler	B-Language
macro	O
instructions	O
describing	O
the	O
configuration	O
to	O
be	O
installed	O
or	O
updated	O
.	O
</s>
<s>
The	O
assembler	B-Language
does	O
not	O
actually	O
compile	O
any	O
object	O
code	O
,	O
but	O
instead	O
compiles	O
a	O
series	O
of	O
PUNCH	O
pseudo-ops	O
in	O
order	O
to	O
generate	O
a	O
job	O
stream	O
for	O
Stage	O
2	O
.	O
</s>
<s>
As	O
IBM	O
changed	O
the	O
nomenclature	O
for	O
OS/360	B-Application
options	O
,	O
it	O
also	O
changed	O
the	O
Sysgen	O
macro	O
definitions	O
to	O
use	O
newer	O
names	O
for	O
the	O
options	O
.	O
</s>
<s>
The	O
Stage	O
2	O
jobstream	O
uses	O
a	O
variety	O
of	O
utilities	O
,	O
including	O
the	O
assembler	B-Language
and	O
linkage	O
editor	O
.	O
</s>
<s>
This	O
process	O
is	O
now	O
obsolete	O
;	O
it	O
was	O
initially	O
replaced	O
by	O
the	O
use	O
of	O
SMP/E	B-Application
,	O
IOCP	B-Application
and	O
MVSCP	O
,	O
then	O
later	O
by	O
SMP/E	B-Application
and	O
Hardware	O
Configuration	O
Definition	O
(	O
HCD	O
)	O
.	O
</s>
