IBM DS8000 User Manual page 217

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 series 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 devices, optional features, and
program products of the input/output
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.
consistency group interval time
The value in seconds that indicates the
length of time between the formation of
consistency groups.
consistent copy
A copy of a data entity (a logical volume,
for example) that contains the contents of
the entire data entity at a single instant in
time.
console
A user interface to a server, for example,
the interface provided on a personal
computer. See also IBM System Storage
Management Console.
contingent allegiance
In mainframe computing, a relationship
that is created in a control unit between a
device and a channel when the channel
accepts unit-check status. The allegiance
causes the control unit to guarantee
access; the control unit does not present
the busy status to the device. The
allegiance enables the channel to retrieve
sense data that is associated with the
unit-check status on the channel path
associated with the allegiance. (GC)
control path
The route that is established from the
master storage unit to the subordinate
storage unit when more than one storage
unit participates in a Global Mirror
session. If there is only one storage unit
(the master) in the Global Mirror session,
no control path is required.
control unit (CU)
1) A device that coordinates and controls
the operation of one or more
input/output devices, and synchronizes
the operation of such devices with the
operation of the system as a whole.
2) For System z, a storage server with
ESCON or OEMI interfaces. The control
unit adapts a native device interface to an
I/O interface that a System z host system
supports.
3) The portion of the storage unit that
supports the attachment of emulated
count key data devices over ESCON,
FICON, or OEMI interfaces. See also
cluster.
control-unit image
In mainframe computing, a logical
subsystem that is accessed through an
ESCON I/O interface. One or more
control-unit images exist in each control
unit. Each image appears as an
independent control unit, but all
control-unit images share a common set
of hardware facilities. The DS8000 series
can emulate 3990-3, TPF, 3990-6, or 2105
control units.
control-unit-initiated reconfiguration (CUIR)
A software mechanism that the DS8000
series uses to request that an operating
system of a System z host verify that one
or more subsystem resources can be taken
offline for service. The DS8000 series can
use this process to automatically vary
channel paths offline and online to
facilitate bay service or concurrent code
installation. Depending on the operating
system, support for this process might be
model dependent, might depend on the
IBM TotalStorage Enterprise Storage
Server Subsystem Device Driver, or might
not exist.
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Glossary