<s>
In	O
databases	O
and	O
transaction	B-General_Concept
processing	I-General_Concept
the	O
term	O
Locks	B-Operating_System
with	I-Operating_System
ordered	I-Operating_System
sharing	I-Operating_System
comprises	O
several	O
variants	O
of	O
the	O
two-phase	B-Operating_System
locking	I-Operating_System
(	O
2PL	O
)	O
concurrency	B-Operating_System
control	I-Operating_System
protocol	O
generated	O
by	O
changing	O
the	O
blocking	O
semantics	O
of	O
locks	O
upon	O
conflicts	O
.	O
</s>
