IBM 990 - Manual (Page 271)

Glossary 259
Small Computer System Interface (SCSI). (1) An
ANSI standard for a logical interface to a computer
peripherals and for a computer peripheral interface.
The interface uses a SCSI logical protocol over an I/O
interface that configures attached targets and initiators
in a multi-drop bus topology. (2) A standard hardware
interface that enables a variety of peripheral devices to
communicate with one another.
spanning channels. MIF spanning channels have the
ability to be configured to multiple Channel SubSystems,
and be transparently shared by any or all of the configured
LPARs without regard to the Logical Channel SubSystem
to which the LPAR is configured.
subchannel. A logical function of a Channel
Subsystem associated with the management of a
single device.
subsystem. (1) A secondary or subordinate system,
or programming support, usually capable of operating
independently of or asynchronously with a controlling
system.
SWCH. In ESCON Manager, the mnemonic used to
represent an ESCON Director.
switch. In ESCON Manager, synonym for ESCON
Director.
trunk cable. In an ESCON environment, a cable
consisting of multiple fiber pairs that do not directly
attach to an active device. This cable usually exists
between distribution panels and can be located within,
or external to, a building. Contrast with jumper cable.
unblocked. In an ESCON Director, the attribute that,
when set, establishes communication capability for a
specific port. Contrast with blocked.
unit address. The ESA/390 term for the address
associated with a device on a given controller. On
ESCON or FICON interfaces, the unit address is the
same as the device address. On OEMI interfaces, the
unit address specifies a controller and device pair on
the interface.
z/Architecture. An IBM architecture for mainframe
computers and peripherals. Processors that follow this
architecture include the zSeries Server family of
processors.