IBM TOTAL STORAGE DS8000 User Manual
Page 364
associating
multiple
devices
of
a
single
control-unit
image
with
a
single
logical
device.
Up
to
eight
device
addresses
can
be
assigned
to
a
PAV.
The
PAV
function
enables
two
or
more
concurrent
write
operations
to
the
same
logical
volume,
as
long
as
the
write
operations
are
not
to
the
same
extents.
See
also
extent,
I/O
Priority
Queueing,
and
multiple
allegiance.
parity
A
data
checking
scheme
used
in
a
computer
system
to
ensure
the
integrity
of
the
data.
The
RAID
implementation
uses
parity
to
re-create
data
if
a
disk
drive
fails.
path
group
In
zSeries
architecture,
a
set
of
channel
paths
that
are
defined
to
a
control
unit
as
being
associated
with
a
single
logical
partition
(LPAR).
The
channel
paths
are
in
a
group
state
and
are
online
to
the
host.
See
also
logical
partition.
path
group
identifier
In
zSeries
architecture,
the
identifier
that
uniquely
identifies
a
given
logical
partition
(LPAR).
The
path
group
identifier
is
used
in
communication
between
the
LPAR
program
and
a
device.
The
identifier
associates
the
path
group
with
one
or
more
channel
paths,
thereby
defining
these
paths
to
the
control
unit
as
being
associated
with
the
same
LPAR.
See
also
logical
partition.
PAV
See
parallel
access
volume.
PCI
See
peripheral
component
interconnect.
PDU
See
protocol
data
unit.
PE
See
IBM
product
engineering.
peripheral
component
interconnect
(PCI)
An
architecture
for
a
system
bus
and
associated
protocols
that
supports
attachments
of
adapter
cards
to
a
system
backplane.
persistent
FlashCopy
A
state
where
a
FlashCopy
relationship
remains
indefinitely
until
the
user
deletes
it.
The
relationship
between
the
source
and
target
volumes
is
maintained
after
a
background
copy
completes.
physical
path
A
single
path
through
the
I/O
interconnection
fabric
that
attaches
two
units.
For
Copy
Services,
this
is
the
path
from
a
host
adapter
on
one
DS8000
(through
cabling
and
switches)
to
a
host
adapter
on
anotherDS8000.
pinned
data
Data
that
is
held
in
cache
until
either
an
error
condition
is
corrected
and
it
can
be
moved
to
disk
storage
or
until
the
data
is
discarded
by
a
host
command.
Pinned
data
conditions
can
only
occur
on
an
ESS
Model
800
during
fast-write
or
dual-copy
functions.
point-in-time
copy
A
FlashCopy
option
that
creates
an
instantaneous
view
of
original
source
data
at
a
specific
moment
in
time.
point-to-point
connection
A
fibre-channel
topology
that
enables
the
direct
interconnection
of
ports.
See
also
arbitrated
loop
and
switched
fabric.
port
A
physical
connection
on
a
host
adapter
to
the
cable
that
connects
the
DS8000
to
hosts,
switches,
or
another
DS8000.
The
DS8000
uses
SCSI
and
ESCON
host
adapters
that
have
two
ports
per
adapter,
and
fibre-channel
host
adapters
that
have
one
port.
See
also
ESCON,
fibre
channel,
host
adapter,
and
small
computer
system
interface.
POST
See
power-on
self
test.
power-on
self
test
(POST)
A
diagnostic
test
that
servers
or
computers
run
when
they
are
turned
on.
predictable
write
A
write
operation
that
can
cache
without
knowledge
of
the
existing
format
on
the
medium.
All
write
operations
on
FBA
DASD
devices
are
predictable.
On
CKD
DASD
devices,
a
write
operation
is
predictable
if
it
does
a
format
write
operation
for
the
first
data
record
on
the
track.
primary
control
unit
The
DS8000
to
which
a
Remote
Mirror
and
Copy
primary
device
is
physically
attached.
processor
complex
A
partition
of
a
storage
server
that
is
capable
of
performing
all
defined
functions
of
the
storage
server.
Multiple
processor
complexes
provide
redundancy.
product
engineering
See
IBM
product
engineering.
344
IBM
TotalStorage
DS8000:
Messages
Reference