<s>
Linux	B-Application
on	I-Application
IBM	I-Application
Z	I-Application
or	O
Linux	B-Application
on	O
zSystems	O
is	O
the	O
collective	O
term	O
for	O
the	O
Linux	B-Application
operating	I-Application
system	I-Application
compiled	O
to	O
run	O
on	O
IBM	B-Device
mainframes	I-Device
,	O
especially	O
IBM	B-Device
Z	I-Device
/	O
IBM	O
zSystems	O
and	O
IBM	B-Application
LinuxONE	I-Application
servers	O
.	O
</s>
<s>
Similar	O
terms	O
which	O
imply	O
the	O
same	O
meaning	O
are	O
Linux/390	B-Application
,	O
Linux/390x	O
,	O
etc	O
.	O
</s>
<s>
The	O
three	O
Linux	B-Application
distributions	O
certified	O
for	O
usage	O
on	O
the	O
IBM	B-Device
Z	I-Device
hardware	O
platform	O
are	O
Red	O
Hat	O
Enterprise	O
Linux	B-Application
,	O
SUSE	O
Linux	B-Application
Enterprise	O
Server	O
,	O
and	O
Ubuntu	B-Operating_System
.	O
</s>
<s>
Linux	B-Application
on	I-Application
IBM	I-Application
Z	I-Application
originated	O
as	O
two	O
separate	O
efforts	O
to	O
port	O
Linux	B-Application
to	O
IBM	O
's	O
System/390	B-Device
servers	O
.	O
</s>
<s>
IBM	O
published	O
a	O
collection	O
of	O
patches	O
and	O
additions	O
to	O
the	O
Linux	B-Application
2.2.13	O
kernel	B-Operating_System
on	O
December	O
18	O
,	O
1999	O
,	O
to	O
start	O
today	O
's	O
mainline	O
Linux	B-Application
on	I-Application
IBM	I-Application
Z	I-Application
.	O
</s>
<s>
Formal	O
product	O
announcements	O
quickly	O
followed	O
in	O
2000	O
,	O
including	O
the	O
Integrated	B-Application
Facility	I-Application
for	I-Application
Linux	I-Application
(	O
IFL	O
)	O
engines	O
.	O
</s>
<s>
Think	O
Blue	O
Linux	B-Application
was	O
an	O
early	O
mainframe	B-Architecture
distribution	O
consisting	O
mainly	O
of	O
Red	O
Hat	O
packages	O
added	O
to	O
the	O
IBM	O
kernel	B-Operating_System
.	O
</s>
<s>
Commercial	O
Linux	B-Application
distributors	O
introduced	O
mainframe	B-Architecture
editions	O
very	O
quickly	O
after	O
the	O
initial	O
kernel	B-Operating_System
work	O
.	O
</s>
<s>
IBM	O
manager	O
Karl-Heinz	O
Strassemeyer	O
of	O
Böblingen	O
in	O
Germany	O
was	O
the	O
main	O
lead	O
to	O
get	O
Linux	B-Application
running	O
on	O
S/390	B-Device
.	O
</s>
<s>
At	O
the	O
start	O
of	O
IBM	O
's	O
involvement	O
,	O
Linux	B-Application
patches	O
for	O
IBM	B-Device
Z	I-Device
included	O
some	O
object	O
code	O
only	O
(	O
OCO	O
)	O
modules	O
,	O
without	O
source	O
code	O
.	O
</s>
<s>
Soon	O
after	O
IBM	O
replaced	O
the	O
OCO	O
modules	O
with	O
open	B-Application
source	I-Application
modules	O
.	O
</s>
<s>
Linux	B-Application
on	I-Application
IBM	I-Application
Z	I-Application
is	O
free	B-Application
software	I-Application
under	O
the	O
GNU	B-License
General	I-License
Public	I-License
License	I-License
.	O
</s>
<s>
According	O
to	O
IBM	O
,	O
by	O
May	O
,	O
2006	O
,	O
over	O
1,700	O
customers	O
were	O
running	O
Linux	B-Application
on	O
their	O
mainframes	B-Architecture
.	O
</s>
<s>
Virtualization	B-General_Concept
is	O
required	O
by	O
default	O
on	O
IBM	B-Device
Z	I-Device
;	O
there	O
is	O
no	O
option	O
to	O
run	O
Linux	B-Application
on	I-Application
IBM	I-Application
Z	I-Application
without	O
some	O
degree	O
of	O
virtualization	B-General_Concept
.	O
</s>
<s>
First	O
layer	O
virtualization	B-General_Concept
is	O
provided	O
by	O
the	O
Processor	O
Resource	O
and	O
System	O
Manager	O
(	O
PR/SM	O
)	O
to	O
deploy	O
one	O
or	O
more	O
Logical	O
Partitions	O
(	O
LPARs	O
)	O
.	O
</s>
<s>
Each	O
LPAR	O
supports	O
a	O
variety	O
of	O
operating	O
systems	O
including	O
Linux	B-Application
on	I-Application
IBM	I-Application
Z	I-Application
.	O
</s>
<s>
A	O
hypervisor	B-Operating_System
called	O
z/VM	B-Application
can	O
also	O
be	O
run	O
as	O
the	O
second	O
layer	O
virtualization	B-General_Concept
in	O
LPARs	O
to	O
create	O
as	O
many	O
virtual	O
machines	O
(	O
VMs	O
)	O
as	O
there	O
are	O
resources	O
assigned	O
to	O
the	O
LPARs	O
to	O
support	O
them	O
.	O
</s>
<s>
KVM	B-Application
on	O
IBM	B-Device
Z	I-Device
is	O
another	O
hypervisor	B-Operating_System
option	O
.	O
</s>
<s>
When	O
Linux	B-Application
applications	O
in	O
an	O
LPAR	O
access	O
data	O
and	O
applications	O
in	O
other	O
LPARs	O
such	O
as	O
CICS	B-Application
,	O
IBM	B-Application
Db2	I-Application
,	O
IMS	B-Application
,	O
Linux	B-Application
,	O
and	O
other	O
mainframe	B-Architecture
subsystems	O
running	O
on	O
the	O
same	O
physical	O
mainframe	B-Architecture
,	O
they	O
can	O
utilize	O
HiperSockets	B-Device
fast	O
,	O
memory-only	O
TCP/IP	B-Protocol
connections	O
.	O
</s>
<s>
As	O
compared	O
to	O
TCP/IP	B-Protocol
over	O
standard	O
network	B-Protocol
interface	I-Protocol
controllers	I-Protocol
(	O
NICs	O
,	O
also	O
known	O
as	O
Open	O
System	O
Adapters	O
(	O
OSAs	O
)	O
in	O
mainframes	B-Architecture
)	O
,	O
HiperSockets	B-Device
can	O
improve	O
end-user	O
responsiveness	O
(	O
reduce	O
network	O
latency	O
and	O
processing	O
overhead	O
)	O
,	O
security	O
(	O
since	O
there	O
's	O
no	O
network	O
connection	O
to	O
intercept	O
)	O
,	O
and	O
reliability	O
(	O
since	O
there	O
's	O
no	O
network	O
connection	O
to	O
lose	O
)	O
.	O
</s>
<s>
With	O
the	O
zEC12	O
,	O
zBC12	O
,	O
and	O
later	O
models	O
,	O
the	O
HiperSocket	B-Device
concept	O
is	O
extended	O
beyond	O
the	O
physical	O
machine	O
boundary	O
via	O
an	O
RDMA	B-Operating_System
over	I-Operating_System
Converged	I-Operating_System
Ethernet	I-Operating_System
(	O
RoCE	O
)	O
adapter	O
to	O
facilitate	O
a	O
secure	O
and	O
high	O
speed	O
inter-system	O
communication	O
.	O
</s>
<s>
Applications	O
in	O
LPAR	O
A	O
in	O
system	O
A	O
can	O
thus	O
use	O
HiperSockets	B-Device
to	O
communicate	O
with	O
applications	O
in	O
LPAR	O
B	O
in	O
system	O
B	O
to	O
ensure	O
the	O
security	O
and	O
performance	O
attributes	O
.	O
</s>
<s>
Beginning	O
with	O
Linux	B-Application
kernel	B-Operating_System
version	O
4.1	O
released	O
in	O
early	O
2015	O
,	O
Linux	B-Application
on	I-Application
IBM	I-Application
Z	I-Application
is	O
only	O
available	O
as	O
a	O
64-bit	B-Device
operating	O
system	O
compatible	O
with	O
z/Architecture	B-Device
mainframes	B-Architecture
.	O
</s>
<s>
Previously	O
Linux	B-Application
on	I-Application
IBM	I-Application
Z	I-Application
was	O
also	O
available	O
as	O
a	O
32-bit	O
operating	O
system	O
,	O
with	O
31-bit	O
addressing	O
,	O
compatible	O
with	O
older	O
model	O
mainframes	B-Architecture
introduced	O
prior	O
to	O
2000	O
's	O
z900	O
model	O
.	O
</s>
<s>
However	O
,	O
the	O
newer	O
64-bit	B-Device
Linux	B-Application
kernel	B-Operating_System
and	O
64-bit	B-Device
Linux	B-Application
on	I-Application
IBM	I-Application
Z	I-Application
distributions	O
are	O
still	O
backward	O
compatible	O
with	O
applications	O
compiled	O
for	O
32-bit	O
Linux	B-Application
on	I-Application
IBM	I-Application
Z	I-Application
.	O
</s>
<s>
Historically	O
the	O
Linux	B-Application
kernel	B-Operating_System
architecture	O
designations	O
were	O
"	O
s390	B-Device
"	O
and	O
"	O
s390x	O
"	O
to	O
distinguish	O
between	O
the	O
32-bit	O
and	O
64-bit	B-Device
Linux	B-Application
on	I-Application
IBM	I-Application
Z	I-Application
kernels	B-Operating_System
respectively	O
,	O
but	O
"	O
s390	B-Device
"	O
now	O
also	O
refers	O
generally	O
to	O
the	O
one	O
Linux	B-Application
on	I-Application
IBM	I-Application
Z	I-Application
kernel	B-Operating_System
architecture	O
.	O
</s>
<s>
Linux	B-Application
runs	O
on	O
standard	O
,	O
general	O
purpose	O
mainframe	B-Architecture
CPs	O
(	O
Central	O
Processors	O
)	O
as	O
well	O
as	O
IFLs	O
(	O
Integrated	B-Application
Facility	I-Application
for	I-Application
Linux	I-Application
)	O
.	O
</s>
<s>
IFLs	O
are	O
mainframe	B-Architecture
processors	O
dedicated	O
to	O
running	O
Linux	B-Application
,	O
either	O
natively	O
or	O
under	O
a	O
hypervisor	B-Operating_System
(	O
z/VM	B-Application
or	O
KVM	B-Application
on	O
IBM	B-Device
Z	I-Device
)	O
.	O
</s>
<s>
Microcode	B-Device
restricts	O
IFLs	O
from	O
running	O
"	O
traditional	O
"	O
workloads	O
,	O
such	O
as	O
z/OS	B-Application
,	O
but	O
they	O
are	O
physically	O
identical	O
to	O
other	O
IBM	B-Device
Z	I-Device
processors	O
.	O
</s>
<s>
Linux	B-Application
on	I-Application
IBM	I-Application
Z	I-Application
gives	O
the	O
flexibility	O
of	O
running	O
Linux	B-Application
with	O
the	O
advantages	O
of	O
fault-tolerant	B-Architecture
mainframe	I-Architecture
hardware	I-Architecture
capable	O
of	O
over	O
90,000	O
I/O	O
operations	O
per	O
second	O
and	O
with	O
a	O
mean	O
time	O
between	O
failure	O
(	O
MTBF	O
)	O
measured	O
in	O
decades	O
.	O
</s>
<s>
Using	O
virtualization	B-General_Concept
,	O
numerous	O
smaller	O
servers	O
can	O
be	O
combined	O
onto	O
one	O
mainframe	B-Architecture
,	O
gaining	O
some	O
benefits	O
of	O
centralization	O
and	O
cost	O
reduction	O
,	O
while	O
still	O
allowing	O
specialized	O
servers	O
.	O
</s>
<s>
Instead	O
of	O
paravirtualization	O
,	O
IBM	B-Device
mainframes	I-Device
use	O
full	B-Architecture
virtualization	I-Architecture
,	O
which	O
permits	O
workload	O
density	O
far	O
greater	O
than	O
paravirtualization	O
does	O
.	O
</s>
<s>
Combining	O
full	B-Architecture
virtualization	I-Architecture
of	O
the	O
hardware	O
plus	O
lightweight	O
Virtual	B-Application
Machine	I-Application
containers	O
that	O
run	O
Linux	B-Application
in	O
isolation	O
(	O
somewhat	O
similar	O
in	O
concept	O
to	O
Docker	B-Language
)	O
result	O
in	O
a	O
platform	O
that	O
supports	O
more	O
virtual	O
servers	O
than	O
any	O
other	O
in	O
a	O
single	O
footprint	O
,	O
which	O
also	O
can	O
lower	O
operating	O
costs	O
.	O
</s>
<s>
Additional	O
savings	O
can	O
be	O
seen	O
from	O
reduced	O
need	O
for	O
floor	O
space	O
,	O
power	O
,	O
cooling	O
,	O
networking	O
hardware	O
,	O
and	O
the	O
other	O
infrastructure	O
needed	O
to	O
support	O
a	O
data	B-Operating_System
center	I-Operating_System
.	O
</s>
<s>
IBM	B-Device
mainframes	I-Device
allow	O
transparent	O
use	O
of	O
redundant	B-Architecture
processor	I-Architecture
execution	I-Architecture
steps	I-Architecture
and	O
integrity	B-Architecture
checking	I-Architecture
,	O
which	O
is	O
important	O
for	O
critical	O
applications	O
in	O
certain	O
industries	O
such	O
as	O
banking	O
.	O
</s>
<s>
Mainframes	B-Architecture
typically	O
allow	O
hot-swapping	B-Device
of	I-Device
hardware	I-Device
,	O
such	O
as	O
processors	O
and	O
memory	O
.	O
</s>
<s>
IBM	B-Device
Z	I-Device
provides	O
fault	O
tolerance	O
for	O
all	O
key	O
components	O
,	O
including	O
processors	O
,	O
memory	O
,	O
I/O	O
Interconnect	O
,	O
power	O
supply	O
,	O
channel	O
paths	O
,	O
network	B-Protocol
cards	I-Protocol
,	O
and	O
others	O
.	O
</s>
<s>
Many	O
industries	O
continue	O
to	O
rely	O
on	O
mainframes	B-Architecture
where	O
they	O
are	O
considered	O
to	O
be	O
the	O
best	O
option	O
in	O
terms	O
of	O
reliability	O
,	O
security	O
,	O
or	O
cost	O
.	O
</s>
<s>
Linux	B-Application
on	I-Application
IBM	I-Application
Z	I-Application
is	O
not	O
generally	O
appropriate	O
on-premises	O
for	O
small	O
businesses	O
that	O
would	O
have	O
fewer	O
than	O
about	O
10	O
distributed	O
Linux	B-Application
servers	O
,	O
although	O
some	O
expensive	O
per-processor	O
licensed	O
software	O
can	O
quickly	O
reduce	O
that	O
rule	O
of	O
thumb	O
.	O
</s>
<s>
In	O
other	O
words	O
,	O
a	O
single	O
IFL	O
running	O
scores	O
of	O
Linux	B-Application
instances	O
still	O
typically	O
counts	O
as	O
one	O
"	O
ordinary	O
"	O
CPU	O
,	O
at	O
the	O
same	O
CPU	O
price	O
,	O
for	O
software	O
licensing	O
.	O
</s>
<s>
Thus	O
,	O
beyond	O
some	O
minimum	O
threshold	O
,	O
Linux	B-Application
on	I-Application
IBM	I-Application
Z	I-Application
can	O
quickly	O
become	O
cost-advantageous	O
when	O
factoring	O
in	O
labor	O
and	O
software	O
costs	O
.	O
</s>
<s>
The	O
cost	O
equation	O
for	O
Linux	B-Application
on	I-Application
IBM	I-Application
Z	I-Application
is	O
not	O
always	O
well	O
understood	O
and	O
is	O
controversial	O
,	O
and	O
many	O
businesses	O
and	O
governments	O
have	O
difficulty	O
measuring	O
,	O
much	O
less	O
basing	O
decisions	O
on	O
,	O
software	O
,	O
labor	O
,	O
and	O
other	O
costs	O
(	O
such	O
as	O
the	O
costs	O
of	O
outage	O
and	O
security	O
breaches	O
)	O
.	O
</s>
<s>
Server	O
centralization	O
,	O
as	O
Linux	B-Application
on	I-Application
IBM	I-Application
Z	I-Application
provides	O
,	O
might	O
reward	O
cooperation	O
with	O
better	O
service	O
and	O
lower	O
costs	O
,	O
but	O
that	O
's	O
not	O
to	O
say	O
that	O
cooperation	O
is	O
always	O
easily	O
accomplished	O
within	O
a	O
corporate	O
bureaucracy	O
.	O
</s>
<s>
Linux	B-Application
on	I-Application
IBM	I-Application
Z	I-Application
also	O
supports	O
less	O
expensive	O
disk	O
storage	O
devices	O
than	O
z/OS	B-Application
because	O
Linux	B-Application
does	O
not	O
require	O
FICON	O
or	O
ESCON	O
attachment	O
,	O
although	O
z/OS	B-Application
may	O
use	O
disk	O
space	O
more	O
efficiently	O
,	O
on	O
balance	O
,	O
due	O
to	O
hardware-assisted	O
database	O
compression	O
common	O
on	O
z/OS	B-Application
and	O
the	O
smaller	O
number	O
of	O
operating	O
system	O
instances	O
z/OS	B-Application
typically	O
requires	O
.	O
</s>
<s>
There	O
are	O
also	O
some	O
operational	O
advantages	O
using	O
some	O
FICON-attached	O
storage	O
with	O
Linux	B-Application
on	I-Application
IBM	I-Application
Z	I-Application
,	O
for	O
example	O
support	O
for	O
z/VM	B-Application
Live	O
Guest	O
Relocation	O
.	O
</s>
<s>
Mainframe	B-Architecture
characteristics	O
are	O
designed	O
for	O
such	O
business	O
workloads	O
as	O
transaction	O
processing	O
(	O
especially	O
in	O
conjunction	O
with	O
concurrent	O
,	O
high	O
volume	O
batch	O
processing	O
)	O
and	O
large	O
database	O
management	O
.	O
</s>
<s>
Mainframe	B-Architecture
design	O
traditionally	O
emphasizes	O
"	O
balanced	O
"	O
performance	O
for	O
all	O
computing	O
elements	O
including	O
input/output	O
,	O
implemented	O
via	O
channel	B-Device
I/O	I-Device
.	O
</s>
<s>
Mainframes	B-Architecture
offload	O
I/O	O
,	O
system	O
accounting	O
,	O
and	O
other	O
non-core	O
computing	O
tasks	O
from	O
the	O
main	O
CPUs	O
as	O
much	O
as	O
possible	O
,	O
and	O
z/Architecture	B-Device
additionally	O
offloads	O
cryptographic	O
calculations	O
.	O
</s>
<s>
In	O
addition	O
,	O
each	O
I/O	O
adapter	O
typically	O
has	O
two	O
PowerPC	B-Architecture
processors	I-Architecture
,	O
and	O
a	O
z13	O
supports	O
hundreds	O
of	O
I/O	O
adapters	O
.	O
</s>
<s>
Historically	O
,	O
mainframes	B-Architecture
in	O
general	O
,	O
and	O
Linux	B-Application
on	I-Application
IBM	I-Application
Z	I-Application
in	O
particular	O
,	O
did	O
not	O
execute	O
"	O
CPU-intensive	O
"	O
single	O
task	O
computations	O
with	O
notably	O
high	O
performance	O
compared	O
to	O
certain	O
other	O
platforms	O
with	O
a	O
few	O
notable	O
exceptions	O
such	O
as	O
cryptographic	O
calculations	O
.	O
</s>
<s>
Supercomputers	B-Architecture
,	O
including	O
Linux-based	O
supercomputers	B-Architecture
,	O
excel	O
at	O
these	O
workloads	O
.	O
</s>
<s>
This	O
bifurcation	O
between	O
mainframes	B-Architecture
and	O
other	O
platforms	O
has	O
significantly	O
blurred	O
in	O
recent	O
years	O
,	O
starting	O
with	O
the	O
introduction	O
of	O
2008	O
's	O
System	O
z10	O
,	O
a	O
machine	O
based	O
on	O
quad-core	O
4.4GHz	O
processors	O
with	O
hardware	O
decimal	O
floating	O
point	O
.	O
</s>
<s>
As	O
mainframe	B-Architecture
processor	O
technology	O
has	O
continued	O
to	O
evolve	O
,	O
and	O
especially	O
with	O
the	O
introduction	O
of	O
the	O
IBM	B-Application
LinuxONE	I-Application
and	O
IBM	O
z13	O
models	O
in	O
2015	O
,	O
IBM	O
has	O
started	O
promoting	O
its	O
mainframes	B-Architecture
as	O
ideal	O
platforms	O
to	O
run	O
real-time	O
analytics	O
and	O
other	O
computationally	O
intensive	O
tasks	O
that	O
mainframes	B-Architecture
did	O
not	O
historically	O
run	O
well	O
.	O
</s>
<s>
Mainframes	B-Architecture
do	O
not	O
provide	O
graphics	O
or	O
sound	O
adapters	O
,	O
and	O
are	O
as	O
such	O
ill-suited	O
for	O
digital	O
media	O
editing	O
or	O
computer-aided	B-Application
design	I-Application
(	O
CAD	B-Application
)	O
except	O
perhaps	O
in	O
support	O
roles	O
(	O
e.g.	O
</s>
<s>
Like	O
all	O
other	O
versions	O
of	O
Linux	B-Application
,	O
Linux	B-Application
on	I-Application
IBM	I-Application
Z	I-Application
is	O
governed	O
by	O
the	O
GPL	B-License
free	B-Application
software	I-Application
license	O
.	O
</s>
<s>
Complete	O
Linux	B-Application
on	I-Application
IBM	I-Application
Z	I-Application
source	O
code	O
is	O
available	O
from	O
numerous	O
parties	O
on	O
a	O
free	O
and	O
equal	O
basis	O
,	O
and	O
architectural	O
support	O
is	O
part	O
of	O
the	O
main	O
Linux	B-Application
kernel	B-Operating_System
effort	O
.	O
</s>
<s>
Though	O
there	O
are	O
no	O
obstacles	O
to	O
running	O
any	O
Linux	B-Application
on	I-Application
IBM	I-Application
Z	I-Application
distribution	O
on	O
an	O
IBM	B-Device
z	I-Device
System	I-Device
,	O
IBM	O
routinely	O
tests	O
three	O
particular	O
Linux	B-Application
on	I-Application
IBM	I-Application
Z	I-Application
distributions	O
:	O
Red	O
Hat	O
,	O
SUSE	O
,	O
and	O
starting	O
in	O
2015	O
,	O
Canonical	O
's	O
Ubuntu	B-Operating_System
Linux	I-Operating_System
.	O
</s>
<s>
Other	O
notable	O
Linux	B-Application
on	I-Application
IBM	I-Application
Z	I-Application
distributions	O
include	O
Debian	O
(	O
upstream	O
for	O
Ubuntu	B-Operating_System
)	O
,	O
Fedora	O
(	O
upstream	O
for	O
RHEL	O
)	O
,	O
Slackware	B-Application
,	O
CentOS	O
,	O
Alpine	O
Linux	B-Application
and	O
Gentoo	B-Application
.	O
</s>
<s>
Nearly	O
every	O
free	O
or	O
open-source	B-Application
software	I-Application
package	O
available	O
for	O
Linux	B-Application
generally	O
is	O
available	O
for	O
Linux	B-Application
on	I-Application
IBM	I-Application
Z	I-Application
,	O
including	O
Apache	B-Application
HTTP	I-Application
Server	I-Application
,	O
Samba	B-Language
,	O
JBoss	B-Language
,	O
PostgreSQL	B-Application
,	O
MySQL	B-Application
,	O
PHP	B-Application
,	O
Python	B-Language
programming	I-Language
language	I-Language
,	O
Concurrent	B-Application
Versions	I-Application
System	I-Application
(	O
CVS	B-Application
)	O
,	O
GNU	B-Application
Compiler	I-Application
Collection	I-Application
(	O
GCC	B-Application
)	O
,	O
LLVM	B-Application
,	O
and	O
Perl	B-Language
,	O
Rust	B-Application
,	O
among	O
many	O
others	O
.	O
</s>
<s>
Red	O
Hat	O
and	O
SUSE	O
offer	O
mainline	O
support	O
for	O
their	O
distributions	O
running	O
Linux	B-Application
on	I-Application
IBM	I-Application
Z	I-Application
.	O
</s>
<s>
Some	O
standard	O
Linux	B-Application
software	O
applications	O
are	O
readily	O
available	O
pre-compiled	O
,	O
including	O
popular	O
closed-source	O
enterprise	O
software	O
packages	O
such	O
as	O
WebSphere	B-Language
,	O
IBM	B-Application
Db2	I-Application
and	O
Oracle	B-General_Concept
databases	I-General_Concept
and	O
applications	O
,	O
SAP	B-Application
R/3	I-Application
,	O
SAP	B-Application
ERP	I-Application
,	O
and	O
IBM	O
's	O
Java	B-Language
Developer	O
's	O
Kit	O
(	O
JDK	O
)	O
,	O
to	O
name	O
only	O
a	O
few	O
.	O
</s>
<s>
IBM	O
offers	O
resources	O
to	O
developers	O
wishing	O
to	O
target	O
Linux	B-Application
for	O
z	B-Device
:	O
</s>
<s>
The	O
Linux	B-Application
Test	O
Drive	O
,	O
a	O
free	O
program	O
granting	O
a	O
single	O
Linux	B-Application
on	I-Application
IBM	I-Application
Z	I-Application
virtual	B-Application
machine	I-Application
for	O
30	O
days	O
.	O
</s>
<s>
The	O
IBM	O
Systems	O
Application	O
Advantage	O
for	O
Linux	B-Application
(	O
Chiphopper	B-Application
)	O
,	O
a	O
developer	O
program	O
to	O
help	O
developers	O
write	O
and	O
publish	O
cross-platform	O
Linux	B-Application
software	O
.	O
</s>
<s>
The	O
Community	O
Development	O
System	O
for	O
Linux	B-Application
on	I-Application
IBM	I-Application
Z	I-Application
(	O
CDSL	O
)	O
program	O
,	O
a	O
platform	O
for	O
providing	O
open	B-Application
source	I-Application
developers	O
a	O
platform	O
for	O
porting	O
to	O
Linux	B-Application
on	I-Application
System	I-Application
z	I-Application
.	O
</s>
<s>
The	O
Linux	B-Application
Remote	O
Development	O
Program	O
,	O
a	O
fee-based	O
extended	O
developer	O
support	O
program	O
.	O
</s>
<s>
Linux	B-Application
on	I-Application
IBM	I-Application
Z	I-Application
supports	O
Unicode	O
and	O
ASCII	B-Protocol
just	O
like	O
any	O
other	O
Linux	B-Application
distributionit	O
is	O
not	O
an	O
EBCDIC-based	O
operating	O
system	O
.	O
</s>
<s>
However	O
,	O
for	O
convenience	O
Linux	B-Application
is	O
able	O
to	O
read	O
kernel	B-Operating_System
parameters	O
in	O
EBCDIC	B-Language
.	O
</s>
<s>
z/VM	B-Application
takes	O
advantage	O
of	O
this	O
capability	O
.	O
</s>
<s>
Porting	O
Linux	B-Application
applications	O
to	O
Linux	B-Application
on	I-Application
IBM	I-Application
Z	I-Application
is	O
fairly	O
straightforward	O
.	O
</s>
<s>
Potential	O
issues	O
include	O
endianness	O
(	O
Linux	B-Application
on	I-Application
IBM	I-Application
Z	I-Application
is	O
big-endian	O
)	O
and	O
reliance	O
on	O
non-portable	O
libraries	O
particularly	O
if	O
source	O
code	O
is	O
not	O
available	O
.	O
</s>
<s>
Programs	O
can	O
be	O
easily	O
cross	B-Application
compiled	I-Application
to	O
z/Architecture	B-Device
binaries	O
on	O
non-mainframe	O
Linux	O
systems	O
.	O
</s>
<s>
There	O
are	O
at	O
least	O
three	O
software-based	O
IBM	B-Device
Z	I-Device
mainframe	B-Architecture
emulators	B-Application
.	O
</s>
<s>
The	O
open	B-Application
source	I-Application
Hercules	B-Application
emulator	I-Application
supports	O
Linux	B-Application
on	I-Application
IBM	I-Application
Z	I-Application
(	O
and	O
can	O
even	O
run	O
on	O
Linux	B-Application
on	I-Application
System	I-Application
z	I-Application
itself	O
)	O
.	O
</s>
<s>
In	O
2010	O
,	O
IBM	O
introduced	O
the	O
Rational	O
Developer	O
for	O
System	B-Device
z	I-Device
Unit	O
Test	O
Feature	O
(	O
now	O
called	O
Rational	O
Development	O
and	O
Test	O
Environment	O
for	O
z	B-Device
,	O
or	O
sometimes	O
RDTz	O
for	O
short	O
)	O
which	O
provides	O
a	O
restricted	O
use	O
execution	O
environment	O
that	O
can	O
run	O
on	O
X86	O
hardware	O
.	O
</s>
<s>
RDTz	O
includes	O
z/OS	B-Application
(	O
with	O
common	O
middleware	O
)	O
and	O
is	O
also	O
compatible	O
with	O
Linux	B-Application
on	I-Application
IBM	I-Application
Z	I-Application
.	O
</s>
