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ESCON. Enterprise Systems Connection Architecture.
An ESA/390 computer peripheral interface. The I/O
interface utilizes ESA/390 logical protocols over a serial
interface that configures attached units to a
communication fabric.
ESCON director. A I/O interface switch that allows the
interconnection of multiple ESCON interfaces in a
distributed-star topology.
ESD. ElectroStatic Discharge.
extended remote copy. A facility of a storage
controller that assists a control program to maintain a
consistent copy of a logical volume on another storage
facility. All modifications of the primary logical volume by
any attached host are presented in order to a single
host which in turn makes these modifications on the
secondary logical volume.
F
failback. Cluster recovery from failover following
repair. Also see cluster.
failover. The routing of all transactions to a second
controller when the first controller fails. Also see cluster.
fast write. A write operation at cache speed that does
not require immediate transfer of data to a DDM. The
subsystem writes the data directly to cache, to
nonvolatile storage, or to both. The data is then
available for destaging. Fast write reduces the time an
application must wait for the I/O operation to complete.
FBA. Fixed Block Address. An architecture for DASD
logical devices that specifies the format of and access
mechanisms for the logical data units on the device.
The logical data unit is a block. All blocks on the device
are the same size (i.e. fixed) and can be accessed
independently,
FC-AL. Fibre Channel - Arbitrated Loop. An
implementation of the fibre channel standard that uses a
ring topology for the communication fabric. Reference
ANSI X3T11/93-275.
FCS. Fibre Channel Standard.
Fibre Channel Standard (FCS). An ANSI standard for
a computer peripheral interface. The I/O interface
defines a protocol for communication over a serial
interface that configures attached units to a
communication fabric. The protocol is defined in two
layers. The IP layer defines basic interconnection
protocols. The upper layer supports one or more logical
protocols (e.g. FCP for SCSI command protocols,
SBCON for ESA/390 command protocols). Reference
ANSI X3.230-199x.
FIFO. First-In First-Out.
firmware. An ordered set of microcode instructions
and data stored in a hardware EPROM. When
microcode software is installed into a hardware
EPROM, it becomes firmware. Firmware cannot be
modified by the user but can be updated by the service
personnel.
First-In First-Out (FIFO). A queuing technique in
which the next item to be retrieved is the item that has
been in the queue for the longest time.
FRU. Field-Replaceable Unit.
H
HA. Home Address, Host Adapter.
hard drive. A storage medium within a storage server
used to maintain information that the storage server
requires.
HDA. Head and Disk Assembly. The portion of a HDD
associated with the medium and the read/write head.
HDD. Head and Disk Device. A disk drive.
hdisk. An AIX term for storage space.
Home Address (HA). A nine-byte field at the
beginning of a track that contains information identifying
the physical track and its association with a cylinder.
host. A computer.
host adapter. A physical sub-unit of a storage
controller, ultra SCSI host card, that provides the
facilities to attach to one or more host I/O interfaces.
host system. A computer.
hot plug. The ability to add or remove a hardware
facility, resource, or FRU to a unit while its power is on.
I
ID. IDentifier.
identifier (ID). A unique name or address that
identifies such things as programs, devices, or systems.
IML. Initial Microcode Load
implicit allegiance. The ESA/390 term for a
relationship that is created in a control unit between a
device and a channel path, or path group, when an I/O
operation is accepted by the device. The allegiance
causes the control unit to guarantee access (i.e. busy
status is not presented) to the device for the remainder
of the channel program over the set of channel paths
associated with the allegiance.
initiator. A SCSI term for the part of a host computer
that communicates with its attached targets.
Glossary of Terms and Abbreviations
247
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