IBM TOTAL STORAGE DS8000 User Manual
Page 348
channel
command
retry
(CCR)
For
zSeries,
the
protocol
used
between
a
channel
and
a
control
unit
that
enables
the
control
unit
to
request
that
the
channel
reissue
the
current
command.
channel
command
word
(CCW)
For
zSeries,
a
data
structure
that
specifies
an
I/O
operation
to
the
channel
subsystem.
channel
path
For
zSeries,
the
interconnection
between
a
channel
and
its
associated
control
units.
channel
subsystem
For
zSeries,
the
part
of
a
host
computer
that
manages
I/O
communication
between
the
program
and
any
attached
control
units.
channel-subsystem
image
For
zSeries,
the
logical
functions
that
a
system
requires
to
perform
the
function
of
a
channel
subsystem.
With
ESCON
multiple
image
facility
(EMIF),
one
channel
subsystem
image
exists
in
the
channel
subsystem
for
each
logical
partition
(LPAR).
Each
image
appears
to
be
an
independent
channel
subsystem
program,
but
all
images
share
a
common
set
of
hardware
facilities.
CKD
See
count
key
data.
CLI
See
command-line
interface.
See
also
Copy
Services
command-line
interface.
cluster
1)
A
partition
capable
of
performing
all
DS8000
functions.
With
two
clusters
in
the
DS8000,
any
operational
cluster
can
take
over
the
processing
of
a
failing
cluster.
2)
In
the
AIX
operating
system,
a
group
of
nodes
within
a
complex.
cluster
processor
complex
(CPC)
The
unit
within
a
cluster
that
provides
the
management
function
for
the
DS8000.
It
consists
of
cluster
processors,
cluster
memory,
and
related
logic.
command-line
interface
(CLI)
An
interface
provided
by
an
operating
system
that
defines
a
set
of
commands
and
enables
a
user
(or
a
script-like
language)
to
issue
these
commands
by
typing
text
in
response
to
the
command
prompt
(for
example,
DOS
commands
or
UNIX
shell
commands).
See
also
Copy
Services
command-line
interface.
compact
disc
An
optically
read
disc,
typically
storing
approximately
660
MB.
CD-ROM
(compact
disc
read-only
memory)
refers
to
the
read-only
format
used
to
distribute
DS8000
code
and
documentation.
compression
1)
The
process
of
eliminating
gaps,
empty
fields,
redundancies,
and
unnecessary
data
to
shorten
the
length
of
records
or
blocks.
2)
Any
encoding
that
reduces
the
number
of
bits
used
to
represent
a
given
message
or
record.
(GC)
computer-electronic
complex
(CEC)
The
set
of
hardware
facilities
associated
with
a
host
computer.
concurrent
copy
A
facility
on
a
storage
server
that
enables
a
program
to
make
a
backup
of
a
data
set
while
the
logical
volume
remains
available
for
subsequent
processing.
The
data
in
the
backup
copy
is
frozen
at
the
point
in
time
that
the
server
responds
to
the
request.
concurrent
installation
of
licensed
internal
code
Process
of
installing
licensed
internal
code
on
a
DS8000
while
applications
continue
to
run.
concurrent
maintenance
Service
that
is
performed
on
a
unit
while
it
is
operational.
concurrent
media
maintenance
Service
performed
on
a
disk
drive
module
(DDM)
without
losing
access
to
the
data.
configure
In
storage,
to
define
the
logical
and
physical
configuration
of
the
input/output
(I/O)
subsystem
through
the
user
interface
that
the
storage
unit
provides
for
this
function.
consistency
group
A
group
of
volumes
participating
in
FlashCopy
relationships
in
a
logical
subsystem,
across
logical
subsystems,
or
across
multiple
storage
units
that
must
be
kept
in
a
consistent
state
to
ensure
data
integrity.
328
IBM
TotalStorage
DS8000:
Messages
Reference