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IBM System/360 System Programmer's Guide

IBM System/360
137 pages
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If
the
nam4ed
data
set
is
stored
on
more
than
20
vol
urnes,
bytes
253-255
of
the
block
contain
the
relative
track
address
of
the
next
block
of
volume
pointers.
Byte
256
contains
a
binary
zero.
Example:
In
the
following
example,
the
list
of
volumes
that
contain
data
set
A.B
is
read
into
main
storage.
The
search
for
the
volume-list
block
starts
on
the
system
residence
volume.
r---------T----------T-------------------------------------------------,
I Name I
Operation
I
Operand
~
~---------+----------+-------------------------------------------------i
I I
LOCATE
I
INDAB
READ
VOLUME-LIST
BLOCK
FOR
I
I I
Check
Exceptional
Returns
CATALOGED
DATA
SET
A.B INTOI
I
INDAB
I
CAMLST
I NAME,AB"LOCAREA
MAIN
STORAGE
AREA
NAMED
I
I
AB
I
DC
I
CL44'A.B'
LOCAREA.
LOCAREA
ALSO
I
I
LOCAREA
I
DS
I
OD
CONTAINS
3-BYTE
TTR
AND
I
I
I
DS
I 265C 6-BYTE SERIAL
NUMBER
I
L
_________
~
___________
~
_________________________________________________
J
The
LOCATE
macro-instruction
points
to
the
CAMLST
macro-instruction.
NAME,
the
first
operand
of
CAMLST,
specifies
that
the
system
is
to
search
the
catalog
for
a
volume-list
tlock
by
using
the
name
of
a
data
set.
AB,
the
second
operand,
specifies
the
main
storage
location
of
a
44-byte
area
into
which
you
have
placed
the
fully
qualified
name
of
a
data
set.
LOCAREA,
the
fourth
operand,
specifies
a
265-byte
area
you
have
reserved
in
main
storage.
After
execution
of
these
macro-instructions,
the
265-byte
area
contains:
the
256-byte
volurre-list
block
for
data
set
A.B,
the
3-byte
relative
track
address
(TTR)
of
the
block
following
the
one
read
into
main
storage,
and
the
6-byte
serial
number
of
the
volume
on
which
the
block
was
found
..
Specifying
the
Name
of
a
Generation
Data
Set
You
specify
the
name
of
a
generation
data
set
by
using
the
fully
qualified
generation
index
name
and
the
relative
generation
number
of
the
data
set.
The
value
of
a
relative
generation
number
reflects
the
position
of
a
data
set
in
a
generation
data
group.
The
following
values
can
be
used:
•
Zero
-
specifies
the
latest
data
set
cataloged
in
a
generation
data
group.
•
Negative
nt~ber
-
specifies
a
data
set
cataloged
before
the
latest
data
set.
•
Positive
number
-
specifies
a
data
set
not
yet
cataloged
in
the
generation
data
group.
When
you
use
zero
or
a
negative
number
as
the
relative
generation
number,
a
volume-list
block
is
read
into
main
storage
and
the
relative
generation
number
is
replaced
by
the
absolute
generation
name.
When
you
USE~
a
positive
number
as
the
relative
generation
number,
an
absolute
generation
name
is
created
and
replaces
the
relative
generation
number.
A
volume-list
block
is
not
read,
since
none
exists
for
these
data
sets.
Example:
In
t.he
following
example,
the
list
of
volumes
that
contain
generation
data
set
A.PAY(-3)
is
read
into
main
storage.
The
search
for
the
volume-list
block
starts
on
the
system
residence
volume.
Maintaining
the
Catalog
and
the
Volume
Table
of
contents
11

Table of Contents

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IBM System/360 Specifications

General IconGeneral
BrandIBM
ModelSystem/360
CategoryDesktop
LanguageEnglish

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