D
daisy-chain
To serially interconnect a series of SCSI
connectors for multiple devices on the
SCSI bus.
data Any representations such as characters or
analog quantities to which meaning is, or
might be, assigned.
data cartridge
A tape cartridge dedicated to storing data.
Contrast with cleaning cartridge.
data compression
See compression.
Data Facility Storage Management Subsystem
(DFSMS)
An operating environment that helps
automate and centralize the management
of storage. To manage storage, DFSMS
provides the storage administrator with
control over data class, storage class,
management class, storage group, and
automatic class selection routine
definitions.
data transfer element (DTE)
In SCSI terms, a tape drive.
data transfer element (DTE) address
In SCSI terms, the physical location of a
tape drive.
data transfer rate
The average number of bits, characters, or
blocks per unit of time that pass between
corresponding equipment in a data
transmission system. The rate is expressed
in bits, characters, or blocks per second,
minute, or hour.
dB Decibel.
dc Direct current.
decibel
A unit of measure that expresses the ratio
of two amounts of electric or acoustic
signal power that is equal to 10 times the
common logarithm of this ratio.
decrypt
To decipher data.
In Cryptographic Support, to convert
ciphertext into plaintext. See also encrypt.
degauss
To make a magnetic tape nonmagnetic by
the use of electrical coils that carry
currents that neutralize the magnetism of
the tape.
degausser
A device that makes magnetic tape
nonmagnetic.
destage
The movement of a cartridge from the
cartridge cache to an HD slot. A destage
occurs automatically when the cartridge
cache is full.
device Any hardware component or peripheral
device, such as a tape drive or tape
library, that can receive and send data.
device driver
A file that contains the code that is
needed to use an attached device.
DFSMS
See Data Facility Storage Management
Subsystem.
diagnostic cartridge
A tape cartridge that enables the detection
and isolation of errors in programs and
faults in equipment.
differential
See high voltage differential.
Direct flight
An automation technology that passes
tape cartridges over intermediary libraries
in a TS3500 tape library shuttle complex.
disable
To make nonfunctional.
door safety switch
On each frame of the TS4500 tape library,
a mechanism that automatically turns off
the power to the cartridge accessor
whenever you open the front door.
drive See tape drive.
drive head
The component that records an electrical
signal onto magnetic tape, or reads a
signal from tape into an electrical signal.
DTE See data transfer element.
dual-gripper transport mechanism
On the cartridge accessor of the TS4500
tape library and mounted on the pivot
assembly, the device that contains the two
grippers that get and put cartridges into
storage slots, drives, or the I/O stations.
Glossary 173
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