Glossary

channel

(1)A system element that controls one channel path, and whose mode of operation depends on the type of hardware attached. Each channel controls an I/O interface between the channel control element and the attached control units (D). (2) Point-to-point link that transports data from one point to the other. (3) A connection or socket on the motherboard to controller card. A motherboard may have only one or two channels (primary and secondary). If a motherboard has only one channel, it may be necessary to add a controller card to create a secondary channel.

channel-attached

(1)Pertaining to direct attachment of devices by data I/O channels to a computer. (2) Pertaining to devices attached to a control unit by cables, not telecommunication lines (D). Synonymous with local.

channel wrap test

Adiagnostic procedure that checks S/390 host-to-director or host-to-switch connectivity by returning the output of the host as input. The test is host-initiated and transmits Fibre Channel frames to a director or switch port. A director or switch port enabled for channel wrapping echoes the frame back to the host.

Class 2 Fibre Channel service

Provides a connectionless (not dedicated) service with notification of delivery or nondelivery between two node ports (N_Ports).

Class 3 Fibre Channel service

Provides a connectionless (not dedicated) service without notification of delivery or nondelivery between two node ports (N_Ports). Synonymous with datagram.

Class F Fibre Channel service

Used by switches to communicate across interswitch links (ISLs) to configure, control, and coordinate a multiswitch fabric.

Class of Fibre Channel service

Defines the level of connection dedication, acknowledgment, and other characteristics of a connection.

command

(1)A character string from an external source to a system that represents a request for system action. (2) A request from a terminal to perform an operation or execute a program. (3) A value sent through an I/O interface from a channel to a control unit that specifies the operation to be performed (D).

communications tray

The communications tray is a sliding tray located in the middle of the Fabricenter cabinet. The communications tray holds the laptop personal computer (PC), zip drive, and zip drive power supply.