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longwave laser adapter
A connector that is used between a host
and the DS8000 to support longwave
fibre-channel communication.
loop The physical connection between a pair of
device adapters in the DS8000. See also
device adapter.
LPAR See logical partition.
LRC See longitudinal redundancy check.
LRU See least recently used.
LSS See logical subsystem.
LUN See logical unit number.
LVM See logical volume manager.
M
machine level control (MLC)
A database that contains the EC level and
configuration of products in the field.
machine reported product data (MRPD)
Product data gathered by a machine and
sent to a destination such as an IBM
support server or RETAIN. These records
might include such information as feature
code information and product logical
configuration information.
mainframe
A computer, usually in a computer center,
with extensive capabilities and resources
to which other computers may be
connected so that they can share facilities.
(T)
maintenance analysis procedure (MAP)
A hardware maintenance document that
gives an IBM service representative a
step-by-step procedure for tracing a
symptom to the cause of a failure.
management console
See IBM TotalStorage Management
Console.
Management Information Base (MIB)
1) A collection of objects that can be
accessed by means of a network
management protocol. (GC)
2) The MIB record conforms to the Open
Systems Interconnection (OSI) standard
defined by the International Organization
for Standardization (ISO) for the exchange
of information. See also simple network
management protocol.
MAP See maintenance analysis procedure.
master storage unit
The physical unit that controls the creation
of consistency groups in a Global Mirror
session. The master storage unit sends
commands to subordinate storage units. A
storage unit can be a master for only one
Global Mirror session. Contrast with
subordinate storage unit.
maximum consistency group drain time
The value in seconds that indicates the
maximum time that writes from the local
site are delayed to the remote site while
the current consistency group is being
formed at the remote site. When this time
is exceeded, the current attempt to form a
consistency group is ended and another
attempt is started. If this time is exceeded
five times, this maximum time is ignored
on the next attempt to form a consistency
group. The default value is the larger of
four minutes or two times the consistency
group interval time if this value is set to
zero.
maximum coordination time
The value in milliseconds that indicates
the maximum time that is allowed for host
I/O to be delayed during the coordination
of the primary volumes of an Global Mirror
session. The default is 50 milliseconds if
this value is set to zero.
MB See megabyte.
MC See IBM TotalStorage Management
Console.
MCA See Micro Channel architecture.
MDM See Multiple Device Manager.
mean time between failures (MTBF)
1) A projection of the time that an
individual unit remains functional. The time
is based on averaging the performance, or
projected performance, of a population of
statistically independent units. The units
operate under a set of conditions or
assumptions.
2) For a stated period in the life of a
functional unit, the mean value of the
lengths of time between consecutive
failures under stated conditions. (I) (A)
medium
For a storage unit, the disk surface on
which data is stored.
Glossary 341