<s>
In	O
an	O
Oracle	B-General_Concept
database	I-General_Concept
,	O
a	O
change	B-Application
vector	I-Application
consists	O
of	O
a	O
single	O
change	O
to	O
a	O
single	O
data	O
block	O
.	O
</s>
<s>
A	O
change	B-Application
vector	I-Application
is	O
the	O
smallest	O
unit	O
of	O
change	O
recorded	O
in	O
a	O
redo	B-Application
log	I-Application
(	O
in	O
its	O
turn	O
,	O
a	O
redo	B-Application
log	I-Application
comprises	O
files	O
in	O
a	O
proprietary	O
format	O
which	O
logs	O
a	O
history	O
of	O
all	O
changes	O
made	O
to	O
the	O
database	O
)	O
.	O
</s>
