IBM DS8000 - ADDITIONAL INFORMATION, User Manual, Page: 215 / 250

application programming interface
An interface that allows an application
program that is written in a high-level
language to use specific data or functions
of the operating system or another
program.
arbitrated loop
A fibre-channel topology that enables the
interconnection of a set of nodes. See also
point-to-point connection and switched fabric.
array
An ordered collection, or group, of
physical devices (disk drive modules) that
is used to define logical volumes or
devices. In the storage unit, an array is a
group of disks that the user designates to
be managed by the RAID technique. See
also redundant array of independent disks.
ASCII (American National Standard Code for
Information Interchange) The standard
code, using a coded character set
consisting of 7-bit coded characters (8 bits
including parity check), that is used for
information interchange among data
processing systems, data communication
systems, and associated equipment. The
ASCII set consists of control characters
and graphic characters. (A) Some
organizations, including IBM, have used
the parity bit to expand the basic code
set.
assigned storage
The space that is allocated to a volume
and that is assigned to a port.
authorized program analysis report (APAR)
A request for correction of a defect in a
current release of an IBM-supplied
program. (GC)
availability
The degree to which a system or resource
is capable of performing its normal
function. See data availability.
B
bay The physical space that is used for
installing SCSI, ESCON, and fibre-channel
host adapter cards. The DS8000 storage
unit has four bays, two in each cluster.
See also service boundary.
bit The smallest unit of computer
information, which has two possible
states that are represented by the binary
digits 0 or 1. See also byte.
block A string of data elements recorded or
transmitted as a unit. The elements may
be characters, words, or physical records.
(GC)
A group of consecutive bytes used as the
basic storage unit in fixed-block
architecture (FBA). All blocks on the
storage device are the same size (fixed
size). See also fixed-block architecture and
data record.
byte
A string that represents a character and
usually consists of eight binary digits that
are treated as a unit. A byte is the
smallest unit of storage that can be
addressed directly. (GC) See also bit.
C
cache A special-purpose buffer storage, smaller
and faster than main storage, used to
hold a copy of instructions and data
obtained from main storage and likely to
be needed next by the processor. (GC)
cache fast write
A form of the fast-write operation in
which the storage server writes the data
directly to cache, where it is available for
later destaging.
cache hit
An event that occurs when a read
operation is sent to the cluster, and the
requested data is found in cache. Contrast
with cache miss.
cache memory
Memory, typically volatile memory, that a
storage server uses to improve access
times to instructions or data. The cache
memory is typically smaller and faster
than the primary memory or storage
medium. In addition to residing in cache
memory, the same data also resides on the
storage devices in the storage unit.
cache miss
An event that occurs when a read
operation is sent to the cluster, but the
data is not found in cache. Contrast with
cache hit.
call home
A communication link established
between the storage product and a service
provider. The storage product can use this
link to place a call to IBM or to another
service provider when it requires service.
Glossary
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