<s>
In	O
computer	B-General_Concept
science	I-General_Concept
,	O
transaction	O
processing	O
is	O
information	O
processing	O
that	O
is	O
divided	O
into	O
individual	O
,	O
indivisible	O
operations	O
called	O
transactions	O
.	O
</s>
<s>
The	O
technology	O
responsible	O
for	O
making	O
the	O
exchange	O
balanced	O
and	O
predictable	O
is	O
called	O
transaction	B-General_Concept
processing	I-General_Concept
.	O
</s>
<s>
Transaction	B-General_Concept
processing	I-General_Concept
systems	O
consist	O
of	O
computer	O
hardware	O
and	O
software	O
hosting	O
a	O
transaction-oriented	O
application	O
that	O
performs	O
the	O
routine	O
transactions	O
necessary	O
to	O
conduct	O
business	O
.	O
</s>
<s>
Since	O
most	O
,	O
though	O
not	O
necessarily	O
all	O
,	O
transaction	B-General_Concept
processing	I-General_Concept
today	O
is	O
interactive	O
,	O
the	O
term	O
is	O
often	O
treated	O
as	O
synonymous	O
with	O
online	B-General_Concept
transaction	I-General_Concept
processing	I-General_Concept
.	O
</s>
<s>
Transaction	B-General_Concept
processing	I-General_Concept
is	O
designed	O
to	O
maintain	O
a	O
system	O
's	O
Integrity	O
(	O
typically	O
a	O
database	O
or	O
some	O
modern	O
filesystems	B-Application
)	O
in	O
a	O
known	O
,	O
consistent	O
state	O
,	O
by	O
ensuring	O
that	O
interdependent	O
operations	O
on	O
the	O
system	O
are	O
either	O
all	O
completed	O
successfully	O
or	O
all	O
canceled	O
successfully	O
.	O
</s>
<s>
Transaction	B-General_Concept
processing	I-General_Concept
links	O
multiple	O
individual	O
operations	O
in	O
a	O
single	O
,	O
indivisible	O
transaction	O
,	O
and	O
ensures	O
that	O
either	O
all	O
operations	O
in	O
a	O
transaction	O
are	O
completed	O
without	O
error	O
,	O
or	O
none	O
of	O
them	O
are	O
.	O
</s>
<s>
If	O
all	O
operations	O
of	O
a	O
transaction	O
are	O
completed	O
successfully	O
,	O
the	O
transaction	O
is	O
committed	B-Language
by	O
the	O
system	O
,	O
and	O
all	O
changes	O
to	O
the	O
database	O
are	O
made	O
permanent	O
;	O
the	O
transaction	O
cannot	O
be	O
rolled	O
back	O
once	O
this	O
is	O
done	O
.	O
</s>
<s>
Transaction	B-General_Concept
processing	I-General_Concept
guards	O
against	O
hardware	O
and	O
software	O
errors	O
that	O
might	O
leave	O
a	O
transaction	O
partially	O
completed	O
.	O
</s>
<s>
If	O
the	O
computer	O
system	O
crashes	O
in	O
the	O
middle	O
of	O
a	O
transaction	O
,	O
the	O
transaction	B-General_Concept
processing	I-General_Concept
system	O
guarantees	O
that	O
all	O
operations	O
in	O
any	O
uncommitted	O
transactions	O
are	O
cancelled	O
.	O
</s>
<s>
Therefore	O
,	O
concurrent	O
implementations	O
of	O
transaction	B-General_Concept
processing	I-General_Concept
is	O
programmed	O
to	O
guarantee	O
that	O
the	O
end	O
result	O
reflects	O
a	O
conflict-free	O
outcome	O
,	O
the	O
same	O
as	O
could	O
be	O
reached	O
if	O
executing	O
the	O
transactions	O
sequentially	O
in	O
any	O
order	O
(	O
a	O
property	O
called	O
serializability	B-Operating_System
)	O
.	O
</s>
<s>
Transaction-processing	O
systems	O
ensure	O
database	O
integrity	O
by	O
recording	O
intermediate	O
states	O
of	O
the	O
database	O
as	O
it	O
is	O
modified	O
,	O
then	O
using	O
these	O
records	O
to	O
restore	O
the	O
database	O
to	O
a	O
known	O
state	O
if	O
a	O
transaction	O
cannot	O
be	O
committed	B-Language
.	O
</s>
<s>
If	O
any	O
part	O
of	O
the	O
transaction	O
fails	O
before	O
it	O
is	O
committed	B-Language
,	O
these	O
copies	O
are	O
used	O
to	O
restore	O
the	O
database	O
to	O
the	O
state	O
it	O
was	O
in	O
before	O
the	O
transaction	O
began	O
.	O
</s>
<s>
It	O
is	O
also	O
possible	O
to	O
keep	O
a	O
separate	O
journal	B-General_Concept
of	O
all	O
modifications	O
to	O
a	O
database	B-Application
management	I-Application
system	I-Application
.	O
</s>
<s>
This	O
is	O
not	O
required	O
for	O
rollback	O
of	O
failed	O
transactions	O
but	O
it	O
is	O
useful	O
for	O
updating	O
the	O
database	B-Application
management	I-Application
system	I-Application
in	O
the	O
event	O
of	O
a	O
database	O
failure	O
,	O
so	O
some	O
transaction-processing	O
systems	O
provide	O
it	O
.	O
</s>
<s>
If	O
the	O
database	B-Application
management	I-Application
system	I-Application
fails	O
entirely	O
,	O
it	O
must	O
be	O
restored	O
from	O
the	O
most	O
recent	O
back-up	O
.	O
</s>
<s>
The	O
back-up	O
will	O
not	O
reflect	O
transactions	O
committed	B-Language
since	O
the	O
back-up	O
was	O
made	O
.	O
</s>
<s>
However	O
,	O
once	O
the	O
database	B-Application
management	I-Application
system	I-Application
is	O
restored	O
,	O
the	O
journal	B-General_Concept
of	O
after	O
images	O
can	O
be	O
applied	O
to	O
the	O
database	O
(	O
rollforward	O
)	O
to	O
bring	O
the	O
database	B-Application
management	I-Application
system	I-Application
up	O
to	O
date	O
.	O
</s>
<s>
The	O
result	O
is	O
a	O
database	O
in	O
a	O
consistent	O
,	O
known	O
state	O
that	O
includes	O
the	O
results	O
of	O
all	O
transactions	O
committed	B-Language
up	O
to	O
the	O
moment	O
of	O
failure	O
.	O
</s>
<s>
The	O
more	O
transactions	O
involved	O
,	O
the	O
more	O
difficult	O
they	O
are	O
to	O
detect	O
,	O
to	O
the	O
point	O
that	O
transaction	B-General_Concept
processing	I-General_Concept
systems	O
find	O
there	O
is	O
a	O
practical	O
limit	O
to	O
the	O
deadlocks	O
they	O
can	O
detect	O
.	O
</s>
<s>
In	O
systems	O
where	O
commit	O
and	O
rollback	O
mechanisms	O
are	O
not	O
available	O
or	O
undesirable	O
,	O
a	O
compensating	B-General_Concept
transaction	I-General_Concept
is	O
often	O
used	O
to	O
undo	O
failed	O
transactions	O
and	O
restore	O
the	O
system	O
to	O
a	O
previous	O
state	O
.	O
</s>
<s>
Transaction	B-General_Concept
processing	I-General_Concept
has	O
these	O
benefits	O
:	O
</s>
<s>
Standard	O
transaction-processing	O
software	O
,	O
such	O
as	O
IBM	O
's	O
Information	B-Application
Management	I-Application
System	I-Application
,	O
was	O
first	O
developed	O
in	O
the	O
1960s	O
,	O
and	O
was	O
often	O
closely	O
coupled	O
to	O
particular	O
database	B-Application
management	I-Application
systems	I-Application
.	O
</s>
<s>
Client	B-Operating_System
–	I-Operating_System
server	I-Operating_System
computing	I-Operating_System
implemented	O
similar	O
principles	O
in	O
the	O
1980s	O
with	O
mixed	O
success	O
.	O
</s>
<s>
However	O
,	O
in	O
more	O
recent	O
years	O
,	O
the	O
distributed	O
client	B-Operating_System
–	I-Operating_System
server	I-Operating_System
model	I-Operating_System
has	O
become	O
considerably	O
more	O
difficult	O
to	O
maintain	O
.	O
</s>
<s>
In	O
addition	O
,	O
most	O
online	O
systems	O
consist	O
of	O
a	O
whole	O
suite	O
of	O
programs	O
operating	O
together	O
,	O
as	O
opposed	O
to	O
a	O
strict	O
client	B-Operating_System
–	I-Operating_System
server	I-Operating_System
model	I-Operating_System
where	O
the	O
single	O
server	O
could	O
handle	O
the	O
transaction	B-General_Concept
processing	I-General_Concept
.	O
</s>
<s>
Today	O
a	O
number	O
of	O
transaction	B-General_Concept
processing	I-General_Concept
systems	O
are	O
available	O
that	O
work	O
at	O
the	O
inter-program	O
level	O
and	O
which	O
scale	O
to	O
large	O
systems	O
,	O
including	O
mainframes	B-Architecture
.	O
</s>
<s>
One	O
effort	O
is	O
the	O
X/Open	O
Distributed	O
Transaction	B-General_Concept
Processing	I-General_Concept
(	O
DTP	O
)	O
(	O
see	O
also	O
Java	B-Language
Transaction	I-Language
API	I-Language
(	O
JTA	O
)	O
.	O
</s>
<s>
However	O
,	O
proprietary	O
transaction-processing	O
environments	O
such	O
as	O
IBM	O
's	O
CICS	B-Application
are	O
still	O
very	O
popular	O
,	O
although	O
CICS	B-Application
has	O
evolved	O
to	O
include	O
open	O
industry	O
standards	O
as	O
well	O
.	O
</s>
<s>
The	O
term	O
extreme	O
transaction	B-General_Concept
processing	I-General_Concept
(	O
XTP	O
)	O
was	O
used	O
to	O
describe	O
transaction	B-General_Concept
processing	I-General_Concept
systems	O
with	O
uncommonly	O
challenging	O
requirements	O
,	O
particularly	O
throughput	O
requirements	O
(	O
transactions	O
per	O
second	O
)	O
.	O
</s>
