IBM eServer zSeries 900 Technical Guide

© Copyright IBM Corp. 2002 307

Glossary

active configuration. In an ESCON environment, the

ESCON Director configuration determined by the

status of the current set of connectivity attributes.

Contrast with

saved configuration

.

allowed. In an ESCON Director, the attribute that,

when set, establishes dynamic connectivity capability.

Contrast with

prohibited

.

American National Standards Institute (ANSI). An

organization consisting of producers, consumers, and

general interest groups, that establishes the

procedures by which accredited organizations create

and maintain voluntary industry standards in the

United States.

ANSI. See

American National Standards Institute

.

APAR. See

authorized program analysis report

.

authorized program analysis report (APAR). A

report of a problem caused by a suspected defect in a

current, unaltered release of a program.

basic mode. A S/390 central processing mode that

does not use logical partitioning. Contrast with logically

partitioned (LPAR) mode.

blocked. In an ESCON Director, the attribute that,

when set, removes the communication capability of a

specific port. Contrast with

unblocked

.

CBY. Mnemonic for an ESCON channel attached to an

IBM 9034 convertor. The 9034 converts from ESCON

CBY signals to parallel channel interface (OEMI)

communication operating in byte multiplex mode (Bus

and Tag). Contrast with

CVC

.

chained. In an ESCON environment, pertaining to the

physical attachment of two ESCON Directors (ESCDs)

to each other.

channel. (1) A processor system element that controls

one channel path, whose mode of operation depends

on the type of hardware to which it is attached. In a

channel subsystem, each channel controls an I/O

interface between the channel control element and the

logically attached control units. (2) In the ESA/390

architecture, the part of a channel subsystem that

manages a single I/O interface between a channel

subsystem and a set of controllers (control units).

channel path (CHP). A single interface between a

central processor and one or more control units along

which signals and data can be sent to perform I/O

requests.

channel path identifier (CHPID). In a channel

subsystem, a value assigned to each installed channel

path of the system that uniquely identifies that path to

the system.

channel subsystem (CSS). Relieves the processor of

direct I/O communication tasks, and performs path

management functions. Uses a collection of

subchannels to direct a channel to control the flow of

information between I/O devices and main storage.

channel-attached. (1) Pertaining to attachment of

devices directly by data channels (I/O channels) to a

computer. (2) Pertaining to devices attached to a

controlling unit by cables rather than by

telecommunication lines.

CHPID. Channel path identifier.

cladding. In an optical cable, the region of low

refractive index surrounding the core. See also

core

and

optical fiber.

CNC. Mnemonic for an ESCON channel used to

communicate to an ESCON-capable device.

configuration matrix. In an ESCON environment, an

array of connectivity attributes that appear as rows and

columns on a display device and can be used to

determine or change active and saved configurations.

connected. In an ESCON Director, the attribute that,

when set, establishes a dedicated connection between

two ESCON ports. Contrast with

disconnected.

connection. In an ESCON Director, an association

established between two ports that provides a physical

communication path between them.

connectivity attribute. In an ESCON Director, the

characteristic that determines a particular element of a

port's status. See

allowed, blocked, connected,

disconnected, prohibited,

and

unblocked.

control unit. A hardware unit that controls the reading,

writing, or displaying of data at one or more

input/output units.

core. (1) In an optical cable, the central region of an

optical fiber through which light is transmitted. (2) In an

optical cable, the central region of an optical fiber that

has an index of refraction greater than the surrounding

cladding material. See also

cladding

and

optical fiber

.