<s>
Prevayler	B-Application
is	O
an	O
open-source	B-Application
(	O
BSD	B-Operating_System
)	O
system-prevalence	B-Application
layer	O
for	O
Java	B-Language
:	O
it	O
transparently	O
persists	O
plain	B-Language
old	I-Language
Java	I-Language
objects	I-Language
.	O
</s>
<s>
It	O
is	O
an	O
in-RAM	O
database	O
backed	O
by	O
snapshots	O
of	O
the	O
system	O
via	O
object	B-Application
serialization	I-Application
,	O
which	O
are	O
loaded	O
after	O
a	O
system	O
crash	O
to	O
restore	O
state	O
.	O
</s>
<s>
Prevayler	B-Application
's	O
development	O
was	O
started	O
by	O
Klaus	O
Wuestefeld	O
.	O
</s>
<s>
Read	O
operations	O
are	O
three	O
to	O
four	O
orders	O
of	O
magnitude	O
faster	O
with	O
Prevayler	B-Application
when	O
compared	O
to	O
traditional	O
database	O
systems	O
since	O
all	O
objects	O
are	O
always	O
in	O
RAM	B-Architecture
and	O
in-process	O
.	O
</s>
<s>
Prevayler	B-Application
requires	O
enough	O
RAM	B-Architecture
to	O
keep	O
the	O
entire	O
system	O
state	O
.	O
</s>
