IBM System storage DS6000 Series, Attachment Manual

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adapter pair (DA pair). See also device
adapter , RAID 5 , and redundant array of
independent disks .
random access
A mode of accessing data on a medium in
a manner that requires the storage device
to access nonconsecutive storage
locations on the medium.
rank One or more arrays that are combined to
create a logically contiguous storage
space.
redundant array of independent disks (RAID)
A methodology of grouping disk drives for
managing disk storage to insulate data
from a failing disk drive.
refresh FlashCopy target volume
An option (previously called incremental
FlashCopy ) of the DS6000 that creates a
point-in-time data copy without copying an
entire volume for each point-in-time copy.
Remote Mirror and Copy
A feature of a storage server that
constantly updates a secondary copy of a
logical volume to match changes made to
a primary logical volume. The primary and
secondary volumes can be on the same
storage server or on separate storage
servers. See also Global Mirror , Metro
Mirror and Global Copy .
remote technical assistance information
network (RETAIN)
The initial service tracking system for IBM
service support, which captures heartbeat
and call-home records. See also support
catcher and support catcher telephone
number .
REQ/ACK
See request for acknowledgment and
acknowledgment .
request for acknowledgment and
acknowledgment (REQ/ACK)
A cycle of communication between two
data transport devices for the purpose of
verifying the connection, which starts with
a request for acknowledgment from one of
the devices and ends with an
acknowledgment from the second device.
The REQ and ACK signals help to provide
uniform timing to support synchronous
data transfer between an initiator and a
target. The objective of a synchronous
data transfer method is to minimize the
effect of device and cable delays.
reserved allegiance
For zSeries, a relationship that is created
in a control unit between a device and a
channel path, or path group, when the
device completes a Sense Reserve
command. The allegiance causes the
control unit to guarantee access (that is,
busy status is not presented) to the
device. Access is over the set of channel
paths that are associated with the
allegiance; access is for one or more
channel programs until the allegiance
ends.
RETAIN
See remote technical assistance
information network .
S
S/390 IBM enterprise servers based on
Enterprise Systems Architecture/390
(ESA/390). S/390 is the currently accepted
shortened form of the original name
System/390 .
S/390 storage
Storage arrays and logical volumes that
are defined as connected to S/390
servers. This term is synonymous with
count-key-data storage.
SAID See system adapter identification number .
SAM See sequential access method .
SAN See storage area network .
SBCON
See Single-Byte Command Code Sets
Connection .
screen
The physical surface of a display device
upon which information is shown to users.
SCSI See small computer system interface .
SCSI device
A disk drive connected to a host through
an I/O interface using the SCSI protocol. A
SCSI device is either an initiator or a
target. See also initiator and small
computer system interface .
SCSI-FCP
Synonym for fibre-channel protocol, a
protocol used to transport data between
an open-systems host and a fibre-channel
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DS6000 Host Systems Attachment Guide