IBM E10, Service Manual, Page: 265 / 279

logical partition mode (LPAR). The ESA/390 term for
a set of facilities that create the programming
environment defined by the ESA/390 architecture. The
term is typically used when there is more than one
LPAR established on a CEC. An LPAR is conceptually
similar to a virtual machine environment except that the
LPAR is a function of the CEC and is not dependent on
an operating system to create the virtual machine
environment.
logical subsystem. The logical functions of a storage
controller that allow one or more host I/O interfaces to
access a set of logical 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, a given set of logical devices is associated with
one and only one logical subsystem.
logical unit. The SCSI term for a logical device.
Logical Unit Number (LUN). The SCSI term for the
field in an Identify 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. For the 2105, you define
this unit of storage; the logical volume resides on a
RAID-5 array, and is spread over 6 + P or 7 + P drives.
LPAR. Logical PARtition mode.
LRU. Least Recently Used.
LUN. Logical Unit Number.
M
Maintenance Analysis Procedure (MAP). Service
personnel use these procedures during maintenance on
a subsystem.
MAP. Maintenance Analysis Procedure.
MB. MegaByte.
MCA. Micro-Channel Architecture.
medium. For a storage facility, this is the disk surface
on which data is stored.
megabyte (MB). A megabyte of storage is 10
⁶
bytes.
A megabyte of memory is 2
²⁰
bytes.
MIB. Management Information Base.
microcode. Stored microinstructions, not available to
users, that perform certain functions. See firmware.
mirrored pair. Two units that contain the same data.
The system refers to them as one entity.
mirroring. In AS/400 systems, the process of writing
the same data to two disk units within the same
auxiliary storage pool at the same time.
MLC. Machine-Level Control. A data bases that
maintains the EC level and configuration of products in
the field.
MTBF. Mean Time Between Failures. A projection of
the time that an individual unit will remain functional
based on averaging the performance or projected
performance of a population of statistically independent
units under as set of operating conditions or
assumptions.
N
ND. Node Descriptor.
NED. Node-Element Descriptor.
NEQ. Node-Element Qualifier.
nondisruptive. The attribute of an action or activity
that does not result in the loss of any existing capability
or resource, from the customer’s view.
non-removable medium. Recording media that
cannot be added to or removed from a storage device.
non-retentive data. Data that the control program can
easily recreated in the event it is lost. The control
program may cache non-retentive write data in volatile
memory.
Non-Volatile Storage (NVS). Typically refers to
non-volatile memory on a processor rather than a
non-volatile storage device. On a storage facility,
non-volatile storage is used to store active write data to
avoid data loss in the event of a power loss.
NQ. Node Qualifier.
NVRAM. NonVolatile Random Access Memory
NVS. Non-Volatile Storage.
O
OEMI. Original Equipment Manufacturer’s Information.
A reference to an IBM standard for a computer
peripheral interface. More specifically, a reference to
IBM S/360 and S/370 Channel to Control Unit Original
Equipment Manufacture’s Information The interface
utilizes ESA/390 logical protocols over an I/O interface
that configures attached units in a multi-drop bus
topology.
open system. A system whose characteristics comply
with standards made available throughout the industry,
and therefore can be connected to other systems that
comply with the same standards.
Glossary of Terms and Abbreviations
249