IBM Enterprise Storage Server 2105 E10 Introduction And Planning Manual page 137

K
KB. See kilobyte .
key field. The second (optional) field of a CKD record.
The key length is specified in the count field. The key
length determines the field length. The program writes
the data in the key field. The subsystem uses this data
to identify or locate a given record.
kilobyte (KB). (1) For processor storage, real, and
virtual storage, and channel volume, 2
(2) For disk storage capacity and communications
volume, 1000 bytes.
KPOH. See thousands of power-on hours .
L
LAN. See local area network .
last-in first-out (LIFO). A queuing technique in which
the next item to be retrieved is the item most recently
placed in the queue. (A)
least recently used (LRU). (1) The algorithm used to
identify and make available the cache space that
contains the least-recently used data. (2) A policy for a
caching algorithm that chooses to remove from cache
the item that has the longest elapsed time since its last
access.
LCU. See logical control unit .
LED. See light-emitting diode .
LIC. See licensed internal code .
licensed internal code (LIC). Microcode that IBM
does not sell as part of a machine, but licenses 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-wired circuitry.
LIFO. See last-in first-out .
light-emitting diode (LED). A semiconductor chip that
gives off visible or infrared light when activated.
link address. On an ESCON interface, the portion of a
source or destination address in a frame that ESCON
uses to route a frame through an ESCON director.
ESCON associates the link address with a specific
switch port that is on the ESCON director. Equivalently,
it associates the link address with the
channel-subsystem or controller-link-level functions that
are attached to the switch port.
link-level facility. The ESCON hardware and logical
functions of a controller or channel subsystem that allow
communication over an ESCON write interface and an
ESCON read interface.
local area network (LAN). A computer network
located on a user's premises within a limited geographic
area.
local e-mail. An e-mail configuration option for storage
servers that are connected to a host-system network
that does not have a domain name server (DNS).
10
or 1024 bytes.
logical address. On an ESCON interface, the portion
of a source or destination address in a frame used to
select a specific channel-subsystem or control-unit
image.
logical control unit (LCU). See controller image .
logical data unit. A unit of storage that is accessible
on a given device.
logical device. A file for conducting input or output
with a physical device, or a file for mapping user I/O
between virtual and real devices.
logical partition (LPAR). A set of functions that create
the programming environment that is defined by the
ESA/390 architecture. ESA/390 architecture uses this
term when more than one LPAR is established on a
processor. An LPAR is conceptually similar to a virtual
machine environment except that the LPAR is a function
of the processor. Also the LPAR does not depend on an
operating system to create the virtual machine
environment.
logical subsystem (LSS). The logical functions of a
storage controller that allow one or more host I/O
interfaces to access a set of devices. The controller
aggregates the devices according to the addressing
mechanisms of the associated I/O interfaces. One or
more logical subsystems exist on a storage controller. In
general, the controller associates a given set of devices
with only one logical subsystem.
logical unit. The open-systems term for a logical disk
drive.
logical unit number (LUN). The SCSI term for the
field in an identifying message that is used to select a
logical unit on a given target.
logical volume. The storage medium associated with
a logical disk drive. A logical volume typically resides on
one or more storage devices. A logical volume is
referred to on an AIX platform as an hdisk, an AIX term
for storage space. A host system logical volume can be
a physical volume.
logical volume manager (LVM). A set of system
commands, library routines, and other tools that allow
the user to establish and control logical volume storage.
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Glossary