NonStop System Glossary

undefined
Pertaining to the use of an incorrect value for data or the incorrect behavior of a program for which
the ISO/IEC IS 9945-1:1990 standard imposes no portability requirements.
undervoltage
A negative change in the amplitude of the voltage.
unicode
A 2-octet (2-byte) character code designed to represent more alphabetic and graphic characters
than allowed by the ASCII character set. When the first octet of a unicode character is zero, the
second octet maps to the ISO 8859-1 (ASCII) character set. Unicode is the standard character set
for encoding characters in implementations of the Java language and is the default character code
set used by several Microsoft Windows operating systems.
uninterruptible power supply (UPS)
The equipment used to provide an uninterruptible source of power to connected equipment if a
main power outage occurs. The basic components of any UPS system are a rectifier/charger that
converts alternating-current (AC) power to direct-current (DC) power, batteries that store the DC
power, and an inverter that converts the DC power back into AC power for distribution to the load.
unitary segment
See segment.
unmount
To make a fileset inaccessible to the users of a node.
unplanned outage
Time during which a computer system is not capable of doing useful work because of an unplanned
interruption. Unplanned interruptions can include failures caused by faulty hardware, operator
error, or disaster.
unshielded twisted pair (UTP)
A transmission medium consisting of two twisted conductors with no cable shielding. Contrast with
shielded twisted pair (STP).
unspecified
Pertaining to the use of a correct value for data or the correct behavior of a program for which
the ISO/IEC IS 9945-1:1990 standard imposes no portability requirements.
UPS
See uninterruptible power supply (UPS).
upward compatibility
The ability of a requester to operate with a server of a later revision level. In this case, the requester
is upward-compatible with the server, and the server is downward-compatible with the requester.
Contrast with downward compatibility.
user code
A logically distinct part of the NonStop operating system that consists of the code for user processes.
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