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edge switch 2/16 service manual Glossary–9
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
A diagnostic 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.