IBM 990 User Manual

Page 268

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IBM

zSeries 990 Technical Guide

initial program load (IPL).

(1) The initialization

procedure that causes an operating system to
commence operation. (2) The process by which a
configuration image is loaded into storage at the
beginning of a work day or after a system malfunction.
(3) The process of loading system programs and
preparing a system to run jobs.

input/output (I/O).

(1) Pertaining to a device whose

parts can perform an input process and an output
process at the same time. (2) Pertaining to a functional
unit or channel involved in an input process, output
process, or both, concurrently or not, and to the data
involved in such a process. (3) Pertaining to input,
output, or both.

input/output configuration data set (IOCDS).

The

data set in the S/390 processor (in the support
element) that contains an I/O configuration definition
built by the input/output configuration program (IOCP).

input/output configuration program (IOCP).

A S/390

program that defines the channels, I/O devices, paths
to the I/O devices, and the addresses of the I/O
devices to a system. The output is normally written to a
S/390 IOCDS.

interface.

(1) A shared boundary between two

functional units, defined by functional characteristics,
signal characteristics, or other characteristics as
appropriate. The concept includes the specification of
the connection of two devices having different
functions. (2) Hardware, software, or both, that links
systems, programs, or devices.

IOCDS.

See Input/Output configuration data set.

IOCP.

See Input/Output configuration control program.

IODF.

The data set that contains the S/390 I/O

configuration definition file produced during the
defining of the S/390 I/O configuration by HCD. Used
as a source for IPL, IOCP, and Dynamic I/O
Reconfiguration.

IPL.

See initial program load.

jumper cable.

In an ESCON and FICON environment,

an optical cable having two conductors that provides
physical attachment between a channel and a
distribution panel or an ESCON Director port or a
control unit/devices, or between an ESCON Director
port and a distribution panel or a control unit/device, or
between a control unit/device and a distribution panel.
Contrast with trunk cable.

LAN.

See local area network.

laser

. A device that produces optical radiation using a

population inversion to provide light amplification by
stimulated emission of radiation

and (generally) an

optical resonant cavity to provide positive feedback.
Laser radiation can be highly coherent temporally, or
spatially, or both.

LC connector.

An optical fibre cable duplex

connector that terminates both jumper cable
fibres into one housing and provides physical
keying for attachment to an LC duplex receptacle.
For technical details, see the NCITS - American
National Standard for Information Technology -
Fibre Channel Standards document FC-PI.

LCSS.

See Logical Channel Subsystem.

LCU.

See Logical Control Unit.

LED.

See light emitting diode.

licensed internal code (LIC).

Microcode that IBM

does not sell as part of a machine, but instead licenses
it to the customer. LIC is implemented in a part of
storage that is not addressable by user programs.
Some IBM products use it to implement functions as
an alternate to hardwire circuitry.

light-emitting diode (LED).

A semiconductor chip that

gives off visible or infrared light when activated.
Contrast Laser.

link address.

On an ESCON or a FICON interface, the

portion of a source or destination address in a frame
that ESCON or FICON uses to route a frame through
an ESCON or FICON director. ESCON and FICON
associates the link address with a specific switch port
that is on the ESCON or FICON director. Note: For
ESCON, there is a one-byte link address. For FICON,
there can be a one-byte or two-byte link address
specified. One-byte link address for a FICON
non-cascade topology and two-byte link address
supports a FICON cascade switch topology.