<s>
Rational	B-Protocol
ClearCase	I-Protocol
is	O
a	O
family	O
of	O
computer	B-Application
software	I-Application
tools	O
that	O
supports	O
software	O
configuration	O
management	O
(	O
SCM	O
)	O
of	O
source	O
code	O
and	O
other	O
software	O
development	O
assets	O
.	O
</s>
<s>
ClearCase	B-Protocol
includes	O
revision	B-Architecture
control	I-Architecture
and	O
forms	O
the	O
basis	O
for	O
configuration	O
management	O
at	O
large	O
and	O
medium-sized	O
businesses	O
,	O
accommodating	O
projects	O
with	O
hundreds	O
or	O
thousands	O
of	O
developers	O
.	O
</s>
<s>
ClearCase	B-Protocol
supports	O
two	O
configuration	O
management	O
models	O
:	O
UCM	O
(	O
Unified	O
Change	O
Management	O
)	O
and	O
base	O
ClearCase	B-Protocol
.	O
</s>
<s>
UCM	O
provides	O
an	O
out-of-the-box	O
model	O
while	O
base	O
ClearCase	B-Protocol
provides	O
a	O
basic	O
infrastructure	O
(	O
UCM	O
is	O
built	O
on	O
base	O
ClearCase	B-Protocol
)	O
.	O
</s>
<s>
ClearCase	B-Protocol
can	O
accommodate	O
large	O
binary	O
files	O
,	O
large	O
numbers	O
of	O
files	O
,	O
and	O
large	O
repository	O
sizes	O
.	O
</s>
<s>
It	O
uses	O
the	O
MultiVersion	B-Protocol
File	I-Protocol
System	I-Protocol
(	O
MVFS	B-Protocol
)	O
which	O
is	O
a	O
virtual	B-Application
file	I-Application
system	I-Application
that	O
displays	O
specific	O
versions	O
of	O
data	O
stored	O
.	O
</s>
<s>
ClearCase	B-Protocol
was	O
developed	O
by	O
Atria	O
Software	O
and	O
first	O
released	O
in	O
1992	O
on	O
Unix	O
and	O
later	O
on	O
Windows	B-Application
.	O
</s>
<s>
Some	O
of	O
the	O
Atria	O
developers	O
had	O
worked	O
on	O
an	O
earlier	O
,	O
similar	O
system	O
:	O
DSEE	O
(	O
Domain	B-Device
Software	O
Engineering	O
Environment	O
)	O
from	O
Apollo	O
Computer	O
.	O
</s>
<s>
IBM	O
continues	O
to	O
develop	O
and	O
market	O
ClearCase	B-Protocol
.	O
</s>
<s>
DSEE	O
introduced	O
many	O
concepts	O
that	O
were	O
adopted	O
by	O
ClearCase	B-Protocol
.	O
</s>
<s>
The	O
Apollo	B-Device
Domain	I-Device
file	O
system	O
allowed	O
special	O
handler	O
programs	O
to	O
intervene	O
during	O
file	O
access	O
.	O
</s>
<s>
DSEE	O
relied	O
heavily	O
on	O
a	O
file	O
that	O
described	O
all	O
the	B-Application
software	I-Application
modules	O
and	O
their	O
dependencies	O
.	O
</s>
<s>
In	O
the	O
absence	O
of	O
the	O
invisible	O
file	O
redirection	O
of	O
the	O
Apollo	B-Device
Domain	I-Device
file	O
system	O
,	O
ClearCase	B-Protocol
uses	O
the	O
virtual	B-Application
file	I-Application
system	I-Application
provided	O
by	O
the	O
MVFS	B-Protocol
feature	O
that	O
is	O
described	O
below	O
.	O
</s>
<s>
Support	O
for	O
derived	B-General_Concept
objects	I-General_Concept
in	O
a	O
view	O
is	O
similar	O
to	O
DSEE	O
's	O
concept	O
.	O
</s>
<s>
The	O
database	O
system	O
that	O
ClearCase	B-Protocol
uses	O
is	O
RDM	B-Application
Embedded	I-Application
from	O
Raima	O
.	O
</s>
<s>
In	O
ClearCase	B-Protocol
terminology	O
,	O
an	O
individual	O
database	O
is	O
called	O
a	O
VOB	O
(	O
Versioned	B-Protocol
Object	I-Protocol
Base	I-Protocol
)	O
.	O
</s>
<s>
Around	O
this	O
layer	O
,	O
a	O
set	O
of	O
interfaces	O
with	O
accompanying	O
tools	O
are	O
used	O
to	O
manage	O
the	O
physical	O
database	O
system	O
,	O
which	O
requires	O
specific	O
Database	B-General_Concept
administrator	I-General_Concept
skills	O
.	O
</s>
<s>
Beginning	O
with	O
version	O
7	O
,	O
the	O
server	O
platform	O
runs	O
Websphere	O
Application	O
Server	O
with	O
a	O
server	O
application	O
called	O
the	O
Change	O
Management	O
Server	O
(	O
CM	O
Server	O
)	O
,	O
which	O
served	O
ClearCase	B-Protocol
clients	O
via	O
the	O
HTTP	O
Protocol	O
.	O
</s>
<s>
(	O
Before	O
version	O
7	O
there	O
was	O
a	O
web	O
service	O
by	O
which	O
users	O
could	O
access	O
ClearCase	B-Protocol
via	O
their	O
browsers	O
.	O
)	O
</s>
<s>
CM	O
server	O
has	O
since	O
been	O
replaced	O
by	O
the	O
ClearCase	B-Protocol
Remote	O
Client	O
Wide-Area	O
Network	O
Server	O
(	O
CCRC	O
WAN	O
server	O
)	O
,	O
which	O
continues	O
to	O
be	O
based	O
on	O
Websphere	O
Application	O
Server	O
.	O
</s>
<s>
A	O
distinguishing	O
feature	O
of	O
ClearCase	B-Protocol
is	O
the	O
MultiVersion	B-Protocol
File	I-Protocol
System	I-Protocol
(	O
MVFS	B-Protocol
)	O
,	O
a	O
proprietary	O
networked	B-Application
filesystem	I-Application
which	O
can	O
mount	O
VOBs	O
as	O
a	O
virtual	B-Application
file	I-Application
system	I-Application
through	O
a	O
dynamic	O
view	O
,	O
selecting	O
a	O
consistent	O
set	O
of	O
versions	O
and	O
enabling	O
the	O
production	O
of	O
derived	B-General_Concept
objects	I-General_Concept
.	O
</s>
<s>
ClearCase	B-Protocol
also	O
supports	O
snapshot	O
views	O
,	O
which	O
are	O
copies	O
of	O
repository	O
data	O
.	O
</s>
<s>
This	O
mode	O
of	O
operation	O
is	O
similar	O
to	O
that	O
of	O
CVS	O
(	O
Concurrent	O
Versions	O
System	O
)	O
software	B-Application
.	I-Application
</s>
<s>
The	O
dynamic	O
and	O
snapshot	O
view	O
types	O
are	O
supported	O
by	O
the	O
ClearCase	B-Protocol
local	O
client	O
(	O
CCLC	O
)	O
.	O
</s>
<s>
The	O
ClearCase	B-Protocol
remote	O
client	O
(	O
CCRC	O
)	O
supports	O
analogous	O
view	O
types	O
:	O
the	O
automatic	O
view	O
and	O
the	O
web	O
view	O
.	O
</s>
<s>
Both	O
are	O
copy-based	O
,	O
but	O
the	O
automatic	O
view	O
uses	O
the	O
MVFS	B-Protocol
to	O
support	O
local	O
,	O
shareable	O
pools	O
of	O
VOB	O
objects	O
.	O
</s>
<s>
From	O
the	O
perspective	O
of	O
the	O
client	O
computer	O
,	O
a	O
ClearCase	B-Protocol
view	O
appears	O
to	O
be	O
just	O
another	O
file	O
system	O
.	O
</s>
<s>
New	O
files	O
and	O
directories	O
created	O
in	O
a	O
ClearCase	B-Protocol
view	O
are	O
referred	O
as	O
"	O
view-private	O
"	O
to	O
indicate	O
that	O
they	O
are	O
specific	O
to	O
the	O
view	O
and	O
not	O
version-controlled	O
.	O
</s>
<s>
At	O
any	O
time	O
,	O
a	O
view-private	O
object	O
can	O
be	O
added	O
to	O
source	B-Architecture
control	I-Architecture
and	O
become	O
a	O
versioned	O
object	O
,	O
rendering	O
it	O
visible	O
to	O
other	O
users	O
.	O
</s>
<s>
Under	O
base	O
ClearCase	B-Protocol
,	O
each	O
view	O
is	O
controlled	O
by	O
its	O
associated	O
configuration	B-Protocol
specification	I-Protocol
,	O
commonly	O
referred	O
to	O
as	O
a	O
config	O
spec	O
.	O
</s>
<s>
This	O
is	O
a	O
collection	B-Language
of	I-Language
rules	I-Language
(	O
stored	O
internally	O
in	O
a	O
text	O
file	O
,	O
but	O
compiled	O
before	O
use	O
)	O
that	O
specifies	O
what	O
element	O
versions	O
(	O
files	O
or	O
directories	O
)	O
are	O
to	O
be	O
displayed	O
in	O
a	O
view	O
.	O
</s>
<s>
To	O
determine	O
which	O
version	O
,	O
if	O
any	O
,	O
of	O
an	O
element	O
should	O
be	O
visible	O
,	O
ClearCase	B-Protocol
traverses	O
the	O
configuration	B-Protocol
specification	I-Protocol
line-by-line	O
from	O
top	O
to	O
bottom	O
,	O
stopping	O
when	O
a	O
match	O
is	O
found	O
and	O
ignoring	O
any	O
subsequent	O
rules	O
.	O
</s>
<s>
A	O
configuration	B-Protocol
specification	I-Protocol
can	O
also	O
reference	O
other	O
configuration	B-Protocol
specifications	I-Protocol
by	O
means	O
of	O
an	O
'	O
include	O
 '	O
statement	O
.	O
</s>
<s>
In	O
the	O
UCM	O
management	O
model	O
,	O
config	O
specs	O
do	O
not	O
need	O
to	O
be	O
created	O
or	O
maintained	O
manually	O
:	O
they	O
are	O
generated	O
and	O
maintained	O
by	O
ClearCase	B-Protocol
UCM	O
operations	O
.	O
</s>
<s>
The	O
networked	B-Application
filesystem	I-Application
provided	O
by	O
MVFS	B-Protocol
allows	O
for	O
build	O
auditing	O
.	O
</s>
<s>
Builds	O
in	O
views	O
that	O
use	O
the	O
MVFS	B-Protocol
can	O
monitor	O
and	O
record	O
file	O
I/O	B-General_Concept
operations	I-General_Concept
performed	O
during	O
the	O
build	O
process	O
and	O
associate	O
each	O
such	O
event	O
with	O
the	O
command	O
that	O
triggered	O
it	O
.	O
</s>
<s>
This	O
allows	O
ClearCase	B-Protocol
to	O
produce	O
a	O
bill-of-materials	O
which	O
it	O
calls	O
a	O
Configuration	O
Record	O
(	O
CR	O
)	O
for	O
all	O
builds	O
and	O
enable	O
traceability	B-Device
for	O
either	O
software	O
configuration	O
management	O
purposes	O
or	O
as	O
part	O
of	O
a	O
larger	O
application	O
lifecycle	O
management	O
process	O
.	O
</s>
<s>
Build	O
auditing	O
is	O
performed	O
with	O
command-line	O
tools	O
such	O
as	O
a	O
built-in	O
make	B-Application
tools	O
(	O
omake	O
,	O
clearmake	O
)	O
or	O
by	O
using	O
the	O
clearaudit	O
command	O
,	O
which	O
can	O
invoke	O
another	O
build	O
tool	O
,	O
such	O
as	O
Unix	O
make	B-Application
(	O
1	O
)	O
.	O
</s>
<s>
The	O
Versioned	B-Protocol
Object	I-Protocol
Base	I-Protocol
(	O
VOB	O
)	O
that	O
stores	O
versions	O
of	O
file	O
elements	O
and	O
directory	O
elements	O
also	O
stores	O
derived	B-General_Concept
objects	I-General_Concept
and	O
metadata	O
associated	O
with	O
these	O
object	O
types	O
.	O
</s>
<s>
Outputs	O
:	O
All	O
derived	B-General_Concept
object	I-General_Concept
(	O
DO	O
)	O
files	O
(	O
and	O
any	O
dependent	O
DOs	O
)	O
produced	O
as	O
a	O
result	O
of	O
the	O
build	O
.	O
</s>
<s>
The	O
dependency	O
information	O
is	O
stored	O
in	O
a	O
configuration	O
record	O
that	O
can	O
be	O
shown	O
for	O
each	O
derived	B-General_Concept
object	I-General_Concept
.	O
</s>
<s>
The	O
MVFS	B-Protocol
allows	O
derived	B-General_Concept
objects	I-General_Concept
that	O
were	O
built	O
in	O
one	O
dynamic	O
view	O
to	O
be	O
automatically	O
"	O
copied	O
"	O
to	O
another	O
dynamic	O
view	O
that	O
requires	O
"	O
exactly	O
the	O
same	O
"	O
derived	B-General_Concept
object	I-General_Concept
.	O
</s>
<s>
Two	O
derived	B-General_Concept
objects	I-General_Concept
are	O
deemed	O
to	O
be	O
"	O
exactly	O
same	O
"	O
if	O
they	O
have	O
the	O
same	O
configuration	O
record	O
(	O
that	O
is	O
,	O
bill	O
of	O
materials	O
)	O
.	O
</s>
<s>
The	O
shareable	O
derived	B-General_Concept
objects	I-General_Concept
are	O
physically	O
present	O
in	O
the	O
VOB	O
server	O
,	O
not	O
in	O
the	O
views	O
that	O
reference	O
them	O
.	O
</s>
<s>
This	O
feature	O
is	O
called	O
winking	O
in	O
derived	B-General_Concept
objects	I-General_Concept
and	O
requires	O
that	O
the	O
clearmake	O
or	O
omake	O
tool	O
is	O
used	O
for	O
builds	O
.	O
</s>
<s>
ClearCase	B-Protocol
dynamic	O
views	O
are	O
slower	O
than	O
local	O
filesystems	O
,	O
even	O
with	O
a	O
good	O
network	O
infrastructure	O
.	O
</s>
<s>
Repeated	O
subsequent	O
builds	O
may	O
run	O
faster	O
,	O
due	O
to	O
build	O
avoidance	O
that	O
is	O
enabled	O
by	O
ClearCase	B-Protocol
's	O
make	B-Application
substitute	O
.	O
</s>
<s>
Because	O
MVFS	B-Protocol
requires	O
server	O
access	O
every	O
time	O
a	O
file	O
is	O
accessed	O
,	O
the	O
performance	O
of	O
the	O
file	O
system	O
depends	O
on	O
server	O
capacity	O
.	O
</s>
<s>
Originally	O
,	O
ClearCase	B-Protocol
supported	O
only	O
full	O
(	O
"	O
fat	O
"	O
)	O
clients	O
running	O
native	O
on	O
Unix	O
and	O
Windows	B-Application
.	O
</s>
<s>
In	O
version	O
7	O
,	O
the	O
ClearCase	B-Protocol
Remote	O
Client	O
(	O
CCRC	O
)	O
was	O
introduced	O
.	O
</s>
<s>
Other	O
Rational	O
Software	B-Application
products	I-Application
,	O
notably	O
ClearQuest	O
and	O
Rational	O
Team	O
Concert	O
,	O
are	O
integrated	O
with	O
ClearCase	B-Protocol
.	O
</s>
<s>
ClearCase	B-Protocol
is	O
also	O
integrated	O
with	O
Microsoft	O
Visual	O
Studio	O
,	O
Cadence	O
Virtuoso	O
,	O
and	O
the	O
Eclipse	O
IDE	O
through	O
a	O
plugin	O
.	O
</s>
<s>
ClearCase	B-Protocol
MultiSite	O
enables	O
developers	O
at	O
different	O
locations	O
to	O
use	O
the	O
same	O
ClearCase	B-Protocol
versioned	B-Protocol
object	I-Protocol
base	I-Protocol
(	O
VOB	O
)	O
.	O
</s>
<s>
Smart-card	O
authentication	O
of	O
ClearCase	B-Protocol
Remote	O
Clients	O
on	O
Windows	B-Application
by	O
CCRC	O
WAN	O
Servers	O
running	O
on	O
Unix	O
and	O
Linux	B-Application
.	O
</s>
<s>
Increased	O
capacity	O
of	O
Windows	B-Application
servers	O
to	O
host	O
more	O
Versioned	B-Protocol
Object	I-Protocol
Bases	I-Protocol
(	O
VOBs	O
)	O
.	O
</s>
<s>
Fine-grained	O
,	O
role-based	O
ACL	O
administration	O
on	O
file	O
system	O
objects	O
(	O
ClearCase	B-Protocol
"	O
elements	O
"	O
)	O
.	O
</s>
<s>
Automatic	O
views	O
,	O
a	O
WAN-friendly	O
view	O
that	O
uses	O
the	O
ClearCase	B-Protocol
multiversion	B-Protocol
file	I-Protocol
system	I-Protocol
(	O
MVFS	B-Protocol
)	O
to	O
provide	O
dynamic	O
access	O
to	O
versions	O
of	O
VOB	O
elements	O
.	O
</s>
<s>
ClearTeam	O
Explorer	O
(	O
CTE	O
)	O
:	O
a	O
single	O
GUI	O
for	O
all	O
ClearCase	B-Protocol
platform	O
,	O
client	O
,	O
and	O
view	O
types	O
.	O
</s>
<s>
(	O
cleartool	O
is	O
the	O
ClearCase	B-Protocol
command-line	O
facility	O
for	O
LAN	O
deployments	O
.	O
)	O
</s>
