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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