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data rate. The rate at which data is transmitted or
received from a device. Interactive applications tend to
require a high data rate, while batch applications can
usually tolerate lower data rates.
data terminal equipment (DTE) port. A port that is
capable of interfacing to a transmission circuit through a
connection to a data communications equipment (DCE)
port. DTE devices with an RS–232 (or EIA–232) port
interface transmit on pin 3, and receive on pin 2 in a
9–pin connector (reversed in 25–pin connectors). See
also data communications equipment (DCE) port.
DB-9 connector. A 9–pin version of the RS–232C port
interface.
DCC. A dc converter.
DCE port. See data communications equipment (DCE)
port.
DDR. Double data rate. See data rate.
defined zone configuration. The complete set of all
zone objects that are defined in the fabric. The defined
configuration can include multiple zone configurations.
See also enabled zone configuration and zone
configuration.
device. Hosts and storage that connect to a switch.
Example devices are servers, redundant array of
independent disks (RAID) arrays, and tape subsystems.
device connection controls. Enables organizations to
bind an individual device port to a set of one or more
switch ports. Device ports are specified by a worldwide
name (WWN) and typically represent host bus adapters
(HBAs) (servers). See also access control lists.
DID. The 3-byte destination ID of the destination
device, in the 0xDomainAreaALPA format.
direct memory access (DMA). The transfer of data
between memory and an input/output device without
processor intervention.
disparity. The relationship of ones and zeros in an
encoded character. Neutral disparity means an equal
number of each, positive disparity means a majority of
ones, and negative disparity means a majority of zeros.
DLS. See dynamic load sharing.
DMA. See direct memory access.
DNS. Distributed name server.
domain_ID. Unique identifier for the switch in a fabric.
Usually automatically assigned by the switch, but can
also be assigned manually. Can be any value between
1—239.
DRAM. See dynamic random access memory.
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IBM TotalStorage SAN Switch: 2109 Model M12 and Model M14 User's Guide
DTE port. See data terminal equipment (DTE) port.
dual fabric. Two identical fabrics that allow
redundancy in the event that one fabric fails. Use a dual
fabric for mission critical applications.
dual-fabric SAN. A storage area network (SAN) that is
composed of two independent fabrics. Synonymous with
multi-fabric SAN. The two-fabric architecture makes
dual-fabric SANs redundant.
DWDM. Dense wavelength digital multiplexing.
dynamic load sharing (DLS). Dynamic distribution of
traffic over available paths. Allows for recomputing of
routes when a fabric port or fabric loop port (Fx_port) or
expansion port (E_port) changes status.
dynamic random access memory (DRAM). A
storage in which the cells require repetitive application
of control signals to retain stored data.
E
edge fabric. A single fabric that uses two or more
switches as a core to interconnect multiple edge
switches. Synonymous with dual-core fabric. See also
resilient core.
edge switch. A switch whose main task is to connect
nodes into the fabric. See also core switch.
E_D_TOV. See error detect timeout value.
EE_credit. See end-to-end credit.
effective zone configuration. The particular zone
configuration that is currently in effect. Only one
configuration can be in effect at once. The effective
configuration is built each time a zone configuration is
enabled.
EIA. Electronic Industries Alliance.
EIA rack. A storage rack that meets the standards set
by the Electronics Industries Alliance (EIA).
electromagnetic compatibility (EMC). The design
and test of products to meet legal and corporate
specifications dealing with the emissions and
susceptibility to frequencies in the radio spectrum.
Electromagnetic compatibility is the ability of various
electronic equipment to operate properly in the intended
electromagnetic environment.
electromagnetic interference (EMI). Waves of
electromagnetic radiation, including but not limited to
radio frequencies, generated by the flow of electric
current.
electrostatic discharge (ESD). The flow of current
that results when objects having a static charge come
into close enough proximity to discharge.
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