<s>
A	O
long-lived	B-General_Concept
transaction	I-General_Concept
is	O
a	O
transaction	B-General_Concept
that	O
spans	O
multiple	O
database	B-General_Concept
transactions	I-General_Concept
.	O
</s>
<s>
The	O
transaction	B-General_Concept
is	O
considered	O
"	O
long-lived	O
"	O
because	O
its	O
boundaries	O
must	O
,	O
by	O
necessity	O
of	O
business	O
logic	O
,	O
extend	O
past	O
a	O
single	O
database	B-General_Concept
transaction	I-General_Concept
.	O
</s>
<s>
A	O
long-lived	B-General_Concept
transaction	I-General_Concept
can	O
be	O
thought	O
of	O
as	O
a	O
sequence	O
of	O
database	B-General_Concept
transactions	I-General_Concept
grouped	O
to	O
achieve	O
a	O
single	O
atomic	O
result	O
.	O
</s>
<s>
A	O
long-lived	B-General_Concept
transaction	I-General_Concept
creates	O
challenges	O
of	O
concurrency	B-Operating_System
control	I-Operating_System
and	O
scalability	B-Architecture
.	O
</s>
<s>
A	O
chief	O
strategy	O
in	O
designing	O
long-lived	B-General_Concept
transactions	I-General_Concept
is	O
optimistic	B-Operating_System
concurrency	I-Operating_System
control	I-Operating_System
with	O
versioning	B-Architecture
.	O
</s>
