Parallel
access
volumes
Parallel
access
volumes
(PAVs)
allow
your
system
to
access
volumes
in
parallel.
A
PAV
capability
represents
a
significant
performance
improvement
by
the
storage
unit
over
traditional
I/O
processing.
With
PAVs,
your
system
can
access
a
single
volume
from
a
single
host
with
multiple
concurrent
requests.
You
must
configure
both
your
storage
unit
and
operating
system
to
use
PAVs.
You
can
use
the
logical
configuration
definition
to
define
PAV-bases,
PAV-aliases,
and
their
relationship
in
the
storage
unit
hardware.
This
unit
address
relationship
creates
a
single
logical
volume,
allowing
concurrent
I/O
operations.
Static
PAVs
are
PAVs
in
which
the
association
between
a
PAV-base
address
and
its
PAV-aliases
is
pre-defined
and
fixed.
That
is,
the
PAV-aliases
of
a
PAV-base
address
remain
unchanged.
Dynamic
PAVs,
on
the
other
hand,
are
PAVs
in
which
the
association
between
a
PAV-base
address
and
its
PAV-aliases
is
dynamic.
The
device
number
types
(PAV-alias
or
PAV-base)
must
match
the
unit
address
types
as
defined
in
the
storage
unit
hardware.
PAVs
can
improve
the
performance
of
large
volumes.
You
get
better
performance
with
one
base
and
two
aliases
on
a
3390
Model
9
than
from
three
3390
Model
3
volumes
with
no
PAV
support.
With
one
base,
it
also
reduces
storage
management
costs
that
are
associated
with
maintaining
large
numbers
of
volumes.
The
alias
provides
an
alternate
path
to
the
base
device.
For
example,
a
3380
or
a
3390
with
one
alias
has
only
one
device
to
write
to,
but
can
use
two
paths.
The
storage
unit
supports
concurrent
or
parallel
data
transfer
operations
to
or
from
the
same
volume
from
the
same
system
or
system
image
for
S/390
or
zSeries
hosts.
An
S/390
with
PAV
software
support
enables
multiple
users
and
jobs
to
simultaneously
access
a
logical
volume.
Read
and
write
operations
can
be
accessed
simultaneously
to
different
domains.
(The
domain
of
an
I/O
operation
is
the
specified
extents
to
which
the
I/O
operation
applies.)
PAV
requirements
for
the
DS8000
Parallel
access
volumes
(PAVs)
can
provide
significant
performance
enhancements
in
S/390
and
zSeries
environments
by
enabling
simultaneous
processing
for
multiple
I/O
operations
to
the
same
logical
volume.
The
following
list
identifies
the
requirements
for
using
PAVs
on
the
DS8000:
v
The
configuration
that
you
create
on
the
DS8000
must
match
the
configuration
that
you
create
using
IOCP
or
HCD.
v
The
control
unit
(CU)
image
numbers
that
exist
on
the
DS8000
depend
on
what
logical
subsystems
(LSSs)
you
configured:
–
The
CU
image
addresses
are
0
-
254.
For
IOCP
and
HCD,
the
CU
addresses
are
hex
00
-
FE.
–
Logical
subsystem
(LSS)
addresses
are
0
-
254.
The
configuration
might
only
have
a
subset
of
these
addresses,
and
the
subset
might
not
be
contiguous.
You
need
to
know
what
CU
images
you
created
before
you
can
update
the
I/O
configuration.
Your
host
system
uses
the
updated
I/O
information
in
order
to
know
what
CU
images
are
on
the
DS8000.
100
DS8000
User’s
Guide
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