IBM TotalStorage DS4300 Installation, User's, And Maintenance Manual page 203

applicable. A command can be issued by typing it on a
command line or selecting it from a menu.
community string. The name of a community
contained in each Simple Network Management
Protocol (SNMP) message.
concurrent download. A method of downloading and
installing firmware that does not require the user to stop
I/O to the controllers during the process.
CRC. See cyclic redundancy check.
CRT. See cathode ray tube.
CRU. See customer replaceable unit.
customer replaceable unit (CRU). An assembly or
part that a customer can replace in its entirety when any
of its components fail. Contrast with field replaceable
unit (FRU).
cyclic redundancy check (CRC). (1) A redundancy
check in which the check key is generated by a cyclic
algorithm. (2) An error detection technique performed at
both the sending and receiving stations.
dac. See disk array controller.
dar. See disk array router.
DASD. See direct access storage device.
data striping. See striping.
default host group. A logical collection of discovered
host ports, defined host computers, and defined host
groups in the storage-partition topology that fulfill the
following requirements:
v Are not involved in specific logical drive-to-LUN
mappings
v Share access to logical drives with default logical
drive-to-LUN mappings
device type. Identifier used to place devices in the
physical map, such as the switch, hub, or storage.
DHCP. See Dynamic Host Configuration Protocol.
direct access storage device (DASD). A device in
which access time is effectively independent of the
location of the data. Information is entered and retrieved
without reference to previously accessed data. (For
example, a disk drive is a DASD, in contrast with a tape
drive, which stores data as a linear sequence.) DASDs
include both fixed and removable storage devices.
direct memory access (DMA). The transfer of data
between memory and an input/output (I/O) device
without processor intervention.
disk array controller (dac). A disk array controller
device that represents the two controllers of an array.
See also disk array router.
disk array router (dar). A disk array router that
represents an entire array, including current and
deferred paths to all logical unit numbers (LUNs) (hdisks
on AIX). See also disk array controller.
DMA. See direct memory access.
domain. The most significant byte in the node port
(N_port) identifier for the fibre-channel (FC) device. It is
not used in the fibre channel-small computer system
interface (FC-SCSI) hardware path ID. It is required to
be the same for all SCSI targets logically connected to
an FC adapter.
DRAM. See dynamic random access memory.
Dynamic Host Configuration Protocol (DHCP). A
protocol defined by the Internet Engineering Task Force
that is used for dynamically assigning Internet Protocol
(IP) addresses to computers in a network.
dynamic random access memory (DRAM). A
storage in which the cells require repetitive application
of control signals to retain stored data.
ECC. See error correction coding.
EEPROM. See electrically erasable programmable
read-only memory.
EISA. See Extended Industry Standard Architecture.
electrically erasable programmable read-only
memory (EEPROM). A type of memory chip which can
retain its contents without consistent electrical power.
Unlike the PROM which can be programmed only once,
the EEPROM can be erased electrically. Because it can
only be reprogrammed a limited number of times before
it wears out, it is appropriate for storing small amounts
of data that are changed infrequently.
electrostatic discharge (ESD). The flow of current
that results when objects that have a static charge
come into close enough proximity to discharge.
environmental service module (ESM) canister. A
component in a storage expansion enclosure that
monitors the environmental condition of the components
in that enclosure. Not all storage subsystems have ESM
canisters.
E_port. See expansion port.
error correction coding (ECC). A method for
encoding data so that transmission errors can be
detected and corrected by examining the data on the
receiving end. Most ECCs are characterized by the
maximum number of errors they can detect and correct.
ESD. See electrostatic discharge.
ESM canister. See environmental service module
canister.
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Glossary