<s>
HSQLDB	B-Application
(	O
Hyper	O
SQL	B-Language
Database	I-Language
)	O
is	O
a	O
relational	B-Application
database	I-Application
management	I-Application
system	I-Application
written	O
in	O
Java	B-Language
.	O
</s>
<s>
It	O
has	O
a	O
JDBC	B-Application
driver	I-Application
and	O
supports	O
a	O
large	O
subset	O
of	O
SQL-92	B-Language
,	O
SQL:2008	B-Language
,	O
SQL:2011	B-Language
,	O
and	O
SQL:2016	B-Language
standards	O
.	O
</s>
<s>
It	O
offers	O
a	O
fast	O
,	O
small	O
(	O
around	O
1300	O
kilobytes	O
in	O
version	O
2.2	O
)	O
database	B-General_Concept
engine	I-General_Concept
which	O
offers	O
both	O
in-memory	B-General_Concept
and	O
disk-based	O
tables	O
.	O
</s>
<s>
Additionally	O
,	O
it	O
includes	O
tools	O
such	O
as	O
a	O
minimal	O
Web	B-Application
server	I-Application
,	O
command	O
line	O
and	O
GUI	O
management	O
tools	O
(	O
can	O
be	O
run	O
as	O
applets	O
)	O
,	O
and	O
a	O
number	O
of	O
demonstration	O
examples	O
.	O
</s>
<s>
It	O
can	O
run	O
on	O
Java	B-Language
runtimes	O
from	O
version	O
1.1	O
upwards	O
,	O
including	O
free	B-Language
Java	I-Language
implementations	I-Language
such	O
as	O
Kaffe	B-Language
.	O
</s>
<s>
HSQLDB	B-Application
is	O
available	O
under	O
a	O
BSD	B-Operating_System
license	I-Operating_System
.	O
</s>
<s>
It	O
is	O
used	O
as	O
a	O
database	O
and	O
persistence	O
engine	O
in	O
many	O
open	B-Application
source	I-Application
software	I-Application
projects	O
,	O
such	O
as	O
descendants	O
of	O
OpenOffice.org	B-Application
Base	I-Application
(	O
i.e.	O
,	O
Apache	B-Application
OpenOffice	I-Application
Base	I-Application
,	O
LibreOffice	B-Operating_System
Base	I-Operating_System
,	O
etc	O
.	O
</s>
<s>
)	O
,	O
and	O
the	O
Jitsi	B-Protocol
VoIP	O
and	O
video-conference	O
client	O
since	O
version	O
2.6	O
.	O
</s>
<s>
It	O
is	O
also	O
used	O
in	O
commercial	O
products	O
,	O
such	O
as	O
Mathematica	B-Language
and	O
InstallAnywhere	O
(	O
starting	O
with	O
version	O
8.0	O
)	O
.	O
</s>
<s>
HSQLDB	B-Application
version	O
2.0	O
has	O
three	O
transaction	O
control	O
modes	O
.	O
</s>
<s>
It	O
supports	O
read	O
committed	O
and	O
serializable	O
transaction	O
isolation	O
levels	O
with	O
table	O
level	O
locks	O
or	O
with	O
multiversion	B-Operating_System
concurrency	I-Operating_System
control	I-Operating_System
(	O
MVCC	O
)	O
,	O
or	O
a	O
combination	O
of	O
locks	O
and	O
MVCC	O
.	O
</s>
<s>
HSQLDB	B-Application
has	O
two	O
main	O
table	O
types	O
used	O
for	O
durable	O
read-write	O
data	O
storage	O
,	O
i.e.	O
,	O
if	O
a	O
transaction	O
has	O
been	O
successfully	O
committed	O
,	O
it	O
is	O
guaranteed	O
that	O
the	O
data	O
will	O
survive	O
system	O
failure	O
and	O
will	O
keep	O
their	O
integrity	O
.	O
</s>
<s>
The	O
default	O
MEMORY	O
type	O
stores	O
all	O
data	O
changes	O
to	O
the	O
disk	O
in	O
the	O
form	O
of	O
a	O
SQL	B-Language
script	I-Language
.	O
</s>
<s>
The	O
HSQLDB	B-Application
engine	O
loads	O
them	O
only	O
partially	O
and	O
synchronizes	O
the	O
data	O
to	O
the	O
disk	O
on	O
transaction	O
commits	O
.	O
</s>
<s>
These	O
tables	O
can	O
participate	O
,	O
for	O
example	O
,	O
in	O
queries	O
with	O
JOINs	O
and	O
simplify	O
spreadsheet	O
processing	O
and	O
read-write	O
non-durable	O
in-memory	B-General_Concept
data	O
storage	O
.	O
</s>
<s>
HSQLDB	B-Application
2.0	O
supports	O
all	O
the	O
core	O
features	O
and	O
many	O
optional	O
features	O
of	O
SQL:2008	B-Language
.	O
</s>
<s>
Advanced	O
features	O
include	O
user-defined	O
SQL	B-Language
procedures	O
and	O
functions	O
,	O
schemas	O
,	O
datetime	O
intervals	O
,	O
updatable	O
views	O
,	O
arrays	O
,	O
lobs	O
,	O
full	O
and	O
lateral	O
joins	O
and	O
set	B-Language
operations	I-Language
.	O
</s>
<s>
Extensions	O
to	O
standard	O
SQL	B-Language
include	O
user-defined	O
aggregate	O
functions	O
.	O
</s>
<s>
Several	O
versions	O
of	O
HSQLDB	B-Application
have	O
been	O
released	O
since	O
2001	O
.	O
</s>
<s>
Early	O
versions	O
were	O
based	O
on	O
the	O
discontinued	O
HypersonicSQL	O
database	B-General_Concept
engine	I-General_Concept
.	O
</s>
<s>
Version	O
2.0	O
,	O
released	O
in	O
2010	O
,	O
is	O
mostly	O
new	O
code	O
,	O
written	O
to	O
conform	O
to	O
Standard	O
SQL	B-Language
and	O
JDBC	B-Language
4	O
Specification	O
.	O
</s>
<s>
Version	O
2.3.2	O
(	O
released	O
in	O
2014	O
)	O
is	O
fully	O
multi-threaded	O
and	O
supports	O
high	O
performance	O
two-phase	B-Operating_System
locking	I-Operating_System
and	O
MVCC	O
(	O
multiversion	B-Operating_System
concurrency	I-Operating_System
control	I-Operating_System
)	O
transaction	O
control	O
models	O
.	O
</s>
