NonStop S-Series System Expansion and Reduction Guide

Glossary
G-Series Common Glossary
Glossary-21
customer-installable system
customer-installable system. A system that does not require specially trained service
providers to install.
customer-replaceable unit (CRU). A unit that can be replaced in the field either by
customers or by qualified personnel trained by HP. CRUs are divided into the
categories of Class 1, Class 2, and Class 3 based on the risk of causing a system
outage if the documented replacement procedure is not followed correctly and how
much CRU-replacement training or experience is advisable. See also Class-1 CRU
,
Class-2 CRU
, Class-3 CRU, and field-replaceable unit (FRU).
cyclic redundancy check (CRC). The most widely used error detection code for ensuring
the integrity of transmitted data. The digits of the CRC are calculated by the sender for
each block of data sent and recalculated by the receiver. (It is a family of mathematical
functions involving computing the quotient and remainder of a polynomial division.) A
CRC is a form of checksum
.
daemon. See demon.
dark site. See unattended site.
data communications equipment (DCE). Equipment that provides all the functions
required to establish, maintain, and terminate a connection and provides the signal
conversion and coding between the data terminal equipment (DTE) and telephone
company lines or data circuits. A DCE is usually a modem.
data link control (DLC). A set of functions associated with Layer 2 of the Open Systems
Interconnection (OSI) reference model. These functions are responsible for reliable
communication between two physically connected nodes.
data link control (DLC) task. Tasks that support the equivalent to Layer 2 of the Open
Systems Interconnection (OSI) reference model. Wide area network (WAN) DLC tasks
execute in the ServerNet wide area network (SWAN) concentrator communications line
interface processor (CLIP), and each WAN DLC task controls one line interface.
data segment. A virtual memory segment holding data. Every process begins with its own
data segments for program global variables and runtime stacks (and for some libraries,
instance data). Additional data segments can be dynamically created. See also flat
segment and selectable segment.
data terminal equipment (DTE). Equipment that constitutes the data source or data sink
and provides for the communication control function protocol. It includes any piece of
equipment at which a communication path begins or ends.
data transparent. Describes software that examines all eight bits of every data byte and
that uses no bit in a data byte for its own purposes. Internationalized applications must
be data transparent.
dB. See decibel (dB).