NonStop System Glossary

CUSTFILE

An EDIT file included on every site update tape (SUT) as $SYSTEM.Annnnnn.CUSTFILE, where

nnnnnn is the system serial number of the target system. The CUSTFILE contains information on

the software products on the SUT, their related files, and the destination and use of each file. HP

customizes information in the CUSTFILE for each customer’s system.

customer engineer (CE)

See service provider.

customer-installable system

A system that does not require specially trained service providers to install.

customer-replaceable unit (CRU)

A unit that can be installed or 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.