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C-92 Sun Confidential: Internal Only 96257
Revision A
H
half-duplex. A communications channel that transmits
data in either direction, but only one direction at a time.
Contrast with full-duplex.
handshake. (1) A signal exchanged between two soft-
ware components that uses characters inserted into a
data stream to indicate when to start or stop sending da-
ta. (2) A voltage or pulse signal exchanged between two
hardware components to establish a valid connection be-
tween two computers.
HBA. Host bus adapter. A printed circuit board that acts
as an interface between a host microprocessor and disk
controller to relieve the host of data storage and retrieval
tasks, to improve data throughput performance.
HDA. Head disk assembly. A sealed enclosure contain-
ing the mechanical parts of a disk drive, including read/
write heads, disk platters, and other non-electronic com-
ponents.
HDI. Head disk interference.
head crash. Mechanical interference that causes a disk
head and platter to make physical contact with each oth-
er in a way that disables, or ‘crashes,’ the head and
HDA. Head crashes can be caused by rough handling,
sudden power loss, and particulates or other contami-
nants on the surface of a disk.
hexadecimal. A base of 16 counting method (0 to 9, A to
F) for the first position.
HIC. Human interface controller.
host path. In VSM, a communication path with four logi-
cal paths between a host and VTSS logical devices.
hot-pluggable. In VSM, capability that allows a CSE to
remove and replace FRUs while power to the FRU is
maintained. This feature allows hardware maintenance
actions and hardware upgrades to proceed without dis-
rupting subsystem availability. See also hot swap
.
hot swap. To remove and replace a system component
(typically one with a redundant backup) while system
power remains on and system operations continue. See
also hot-pluggable. Contrast with cold swap.
HSC. Host Software Component. The portion of the Sun
StorageTek Automated Cartridge System (ACS) that
serves as an interface between the host operating sys-
tem(s) and the rest of the automated library.
HSM. Hierarchical Storage Manager.
HSSDC. High Speed Serial Data Connector.
HTTP. Hyper Text Transfer Protocol, Hyper Text Trans-
port Protocol. The protocol most often used to transfer
information from World Wide Web servers to browsers.
Hz. Hertz. The number of cycles per second in an elec-
tromagnetic wave; one hertz equals one cycle.
I
ICEn. Iceberg Channel ESCON card used in VSM4-
VTSS and earlier units.
IEC. International Electrotechnical Commission. An or-
ganization in Geneva, Switzerland that sets international
standards for the electrical and electronics fields. IEC
created the Joint Technical Committee for information
technology with ISO.
IEEE. Institute of Electrical and Electronic Engineers. A
worldwide professional organization that sets standards
for telecommunications and computing applications.
IFCMB.VTSS Iceberg Fibre Channel Motherboard
IFES. VTSS Iceberg Fibre-channel Enclosure Services
card
IFF. VTSS Iceberg Fibre-channel Freezer card
IFMZ. Iceberg Fiber-channel Mezzanine card; sub-com-
ponent of IFES card.
IFPB. Iceberg Fiber-channel Port Bypass card; sub-com-
ponent of IFES card.
IML. Initial microcode load, a.k.a. initial microprogram
load. The loading of an operating instruction set, typically
from external media such as a floppy diskette, into the
microprocessor control store of a machine.
impedance. (1) The combined effect of resistance, in-
ductance, and capacitance on a signal at a given fre-
quency. (2) The total opposition (resistance or reactance)
that a circuit offers to the flow of alternating current (AC),
using ohms (Ω) as the unit of measure. A lower ohm val-
ue indicates a better-quality conductor.
interface. (1) A shared boundary where two or more
systems meet. (2) The means by which communication
is achieved at this shared boundary. An interface can be
between hardware and hardware (such as sockets and
plugs, or electrical signals), hardware and software, soft-
ware and software, human and computer (such as a
mouse or keyboard and display screen).
interoperability. Ability to communicate, execute pro-
grams, and transfer data across a variety of hardware
and software platforms from different manufacturers.
interrupt. A temporary suspension of a process. Two
main sources of interrupts are: a signal from outside the
computer, such as someone touching the keyboard or
mouse (hardware interrupt); or a machine instruction
such as a request for input or output (software interrupt).
intranet. A local-area network that functions like the In-
ternet, using web browser software to access and pro-
cess information for employees, and which is located on
computers within a company. An intranet may or may not
be connected to the Internet through web servers.
I/O. Input/output. The movement of data between a host
system and another device.
IPL. Initial program load. See initial microcode load
.
IPXn. Power PC functional microprocessor card.
IS. Information systems; information services.
ISO. International Organization for Standardization. A
voluntary organization comprised of the national stan-
dards organizations of many countries which is responsi-
ble for creating international standards in many areas, in-
cluding computers and communications. ANSI
(American National Standards Institute) is the U.S. mem-
ber of ISO. ISO produced OSI (Open Systems Intercon-
nection), a seven-layer model for network architecture.
ISPn. VSMn-VTSS Iceberg Support Processor card.
IT. Information technology.
ITCC. Iceberg Tray Cable Crossover.