<s>
In	O
IBM	B-Device
mainframe	I-Device
operating	B-General_Concept
systems	I-General_Concept
,	O
basic	B-Application
partitioned	I-Application
access	I-Application
method	I-Application
(	O
BPAM	B-Application
)	O
is	O
an	O
access	B-Application
method	I-Application
for	O
libraries	B-Library
,	O
called	O
partitioned	O
datasets	O
(	O
PDSes	O
)	O
in	O
IBM	O
terminology	O
.	O
</s>
<s>
BPAM	B-Application
is	O
used	O
in	O
OS/360	B-Application
,	O
OS/VS2	B-Application
,	O
MVS	B-Application
,	O
z/OS	B-Application
,	O
and	O
others	O
.	O
</s>
<s>
A	O
PDS	O
consists	O
of	O
members	O
(	O
internally	O
identical	O
to	O
sequential	B-Application
data	I-Application
sets	I-Application
)	O
,	O
registered	O
in	O
a	O
list	O
called	O
the	O
directory	O
.	O
</s>
<s>
Partitioned	O
datasets	O
can	O
store	O
any	O
type	O
of	O
data	O
,	O
but	O
they	O
are	O
often	O
used	O
to	O
store	O
executable	B-Application
programs	I-Application
,	O
or	O
load	O
modules	O
,	O
sometimes	O
called	O
binaries	O
in	O
other	O
systems	O
.	O
</s>
<s>
Other	O
uses	O
include	O
system	O
assembler	O
macro	O
definitions	O
,	O
job	B-Application
control	I-Application
procedures	O
,	O
and	O
program	O
source	O
code	O
.	O
</s>
<s>
BPAM	B-Application
provides	O
an	O
application	B-Application
program	I-Application
interface	I-Application
(	O
API	B-Application
)	O
to	O
allow	O
programmers	O
to	O
access	O
libraries	B-Library
directly	O
.	O
</s>
<s>
The	O
BPAM	B-Application
API	B-Application
is	O
similar	O
to	O
basic	B-Application
sequential	I-Application
access	I-Application
method	I-Application
(	O
BSAM	O
)	O
,	O
but	O
it	O
adds	O
functionality	O
to	O
process	O
directories	O
.	O
</s>
<s>
Individual	O
members	O
of	O
a	O
PDS	O
can	O
also	O
be	O
processed	O
using	O
sequential	O
access	B-Application
methods	I-Application
by	O
specifying	O
the	O
member	O
name	O
on	O
the	O
job	B-Application
control	I-Application
DD	O
statement	O
.	O
</s>
<s>
The	O
programmer	O
specifies	O
DSORG	B-Application
=	O
PO	O
in	O
their	O
Data	B-Application
Control	I-Application
Block	I-Application
(	O
DCB	O
)	O
to	O
indicate	O
use	O
of	O
BPAM	B-Application
.	O
</s>
<s>
As	O
a	O
basic	O
access	B-Application
method	I-Application
BPAM	B-Application
reads	O
and	O
writes	O
member	O
data	O
in	O
blocks	B-General_Concept
and	O
the	O
I/O	O
operation	O
proceeds	O
asynchronously	B-Architecture
and	O
must	O
be	O
tested	O
for	O
completion	O
using	O
the	O
CHECK	O
macro	O
.	O
</s>
<s>
BPAM	B-Application
uses	O
the	O
standard	O
system	O
macros	O
OPEN	O
,	O
CLOSE	O
,	O
READ	O
,	O
WRITE	O
,	O
and	O
CHECK	O
.	O
</s>
<s>
The	O
operating	B-General_Concept
system	I-General_Concept
requires	O
all	O
executable	B-Application
programs	I-Application
to	O
be	O
stored	O
in	O
libraries	B-Library
because	O
the	O
member	O
's	O
directory	O
entry	O
contains	O
additional	O
attribute	O
information	O
specific	O
to	O
load	O
modules	O
.	O
</s>
<s>
Executable	B-Application
programs	I-Application
are	O
written	O
to	O
libraries	B-Library
by	O
the	O
linkage	O
editor	O
and	O
loaded	O
into	O
user-acquired	O
storage	O
by	O
the	O
Loader	O
(	O
an	O
application	O
program	O
)	O
or	O
into	O
system-acquired	O
storage	O
by	O
Program	O
Fetch	O
(	O
a	O
component	O
of	O
the	O
OS	O
supervisor	B-Operating_System
)	O
.	O
</s>
<s>
This	O
organization	O
allows	O
a	O
load	O
module	O
to	O
be	O
completely	O
loaded	O
and	O
relocated	O
with	O
one	O
input/output	O
operation	O
by	O
Program	O
Fetch	O
(	O
EXCP	B-Application
on	O
pre-MVS	O
systems	O
,	O
or	O
STARTIO	B-Application
on	O
MVS/370	O
and	O
later	O
systems	O
)	O
.	O
</s>
