<s>
In	O
database	O
management	O
systems	O
,	O
block	B-General_Concept
contention	I-General_Concept
(	O
or	O
data	O
contention	O
)	O
refers	O
to	O
multiple	O
processes	O
or	O
instances	O
competing	O
for	O
access	O
to	O
the	O
same	O
index	O
or	O
data	O
block	B-General_Concept
at	O
the	O
same	O
time	O
.	O
</s>
<s>
Concurrent	O
statement	O
executions	O
by	O
two	O
or	O
more	O
instances	O
may	O
also	O
lead	O
to	O
contention	O
,	O
and	O
subsequently	O
busy	B-Operating_System
waiting	I-Operating_System
for	O
the	O
process	O
without	O
the	O
lock	B-Operating_System
.	O
</s>
<s>
To	O
reduce	O
contention	O
for	O
table	O
blocks	O
due	O
to	O
delete	O
,	O
select	O
or	O
update	O
statements	O
,	O
reduce	O
the	O
number	O
of	O
rows	O
per	O
block	B-General_Concept
.	O
</s>
<s>
This	O
can	O
be	O
done	O
by	O
using	O
a	O
smaller	O
block	B-General_Concept
size	I-General_Concept
.	O
</s>
<s>
To	O
reduce	O
contention	O
for	O
index	O
blocks	O
the	O
best	O
strategy	O
is	O
to	O
implement	O
a	O
reverse	B-Data_Structure
index	I-Data_Structure
.	O
</s>
