IBM 990 256

6947glos.fm Draft Document for Review April 7, 2004 6:15 pm

256 IBM eServer 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 to a system the channels, I/O

devices, paths to the I/O devices, and the addresses of

the I/O devices.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 hous-

ing 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 hard-wire 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 FICPON 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.