<s>
Telecommunications	B-Application
Access	I-Application
Method	I-Application
(	O
TCAM	O
)	O
is	O
an	O
access	B-Application
method	I-Application
,	O
in	O
IBM	O
's	O
OS/360	B-Application
and	I-Application
successors	I-Application
computer	O
operating	O
systems	O
on	O
IBM	B-Application
System/360	I-Application
and	O
later	O
,	O
that	O
provides	O
access	O
to	O
terminals	O
units	O
within	O
a	O
teleprocessing	O
network	O
.	O
</s>
<s>
TCAM	O
provides	O
similar	O
functionality	O
to	O
QTAM	B-Application
,	O
which	O
it	O
replaced	O
.	O
</s>
<s>
It	O
was	O
the	O
access	B-Application
method	I-Application
for	O
the	O
initial	O
version	O
of	O
Time	B-Application
Sharing	I-Application
Option	I-Application
(	O
TSO	O
)	O
.	O
</s>
<s>
With	O
the	O
advent	O
of	O
IBM	O
's	O
SNA	B-Architecture
,	O
TCAM	O
was	O
eventually	O
superseded	O
by	O
VTAM	B-Application
.	O
</s>
<s>
TCAM	O
was	O
said	O
to	O
have	O
the	O
following	O
enhancements	O
over	O
QTAM	B-Application
:	O
</s>
<s>
Improved	O
organization	O
of	O
message	B-Operating_System
queuing	I-Operating_System
on	O
disk	O
including	O
multiple	O
volume	O
support	O
.	O
</s>
<s>
"	O
Significantly	O
increases	O
speed	O
and	O
efficiency	O
over	O
QTAM.	O
"	O
</s>
<s>
Binary	B-Protocol
Synchronous	I-Protocol
Support	O
.	O
</s>
<s>
This	O
is	O
similar	O
in	O
concept	O
to	O
the	O
much	O
later	O
internet	O
service	O
daemon	O
(	O
inetd	B-Protocol
)	O
in	O
unix	O
and	O
other	O
systems	O
.	O
</s>
<s>
It	O
is	O
also	O
similar	O
to	O
QTAM	B-Application
,	O
where	O
the	O
application	O
programs	O
are	O
called	O
Message	O
Processing	O
Programs	O
(	O
MPP	O
)	O
.	O
</s>
<s>
These	O
macros	O
define	O
the	O
lines	O
and	O
terminals	O
comprising	O
the	O
system	O
,	O
the	O
datasets	B-Application
required	O
,	O
and	O
the	O
procedures	O
used	O
to	O
process	O
received	O
and	O
transmitted	O
messages	O
.	O
</s>
<s>
The	O
application	O
programs	O
,	O
incorporating	O
logic	O
to	O
process	O
the	O
various	O
messages	O
,	O
are	O
supplied	O
by	O
the	O
installation	O
,	O
and	O
use	O
standard	O
OS/360	B-Application
data	O
management	O
macros	O
OPEN	O
and	O
CLOSE	O
,	O
and	O
either	O
the	O
Basic	O
macros	O
READ	O
,	O
WRITE	O
,	O
and	O
CHECK	O
,	O
or	O
the	O
Queued	O
macros	O
GET	O
and	O
PUT	O
.	O
</s>
<s>
The	O
use	O
of	O
SAM	B-General_Concept
macros	O
allows	O
application	O
programs	O
to	O
be	O
tested	O
in	O
a	O
batch	B-General_Concept
processing	I-General_Concept
environment	O
.	O
</s>
<s>
Support	O
for	O
3270	B-Operating_System
terminals	I-Operating_System
was	O
soon	O
added	O
.	O
</s>
