Specifications

PTF. See program temporary fix.
PV Links. Short for Physical Volume Links, an
alternate pathing solution from Hewlett-Packard
providing for multiple paths to a volume, as well as
static load balancing.
R
rack. See enclosure.
RAID. See redundant array of inexpensive disks and
array. RAID also is expanded to redundant array of
independent disks.
RAID 5. A type of RAID that optimizes cost-effective
performance through data striping. RAID 5 provides
fault tolerance for up to two failed disk drives by
distributing parity across all of the drives in the array
plus one parity disk drive. The ESS automatically
reserves spare disk drives when it assigns arrays to a
device adapter pair (DA pair). See device adapter.
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.
redundant array of inexpensive disks (RAID). A
methodology of grouping disk drives for managing disk
storage to insulate data from a failing disk drive.
remote technical assistance information network
(RETAIN). The initial service tracking system for IBM
service support, which captures heartbeat and
call-home records. See support catcher and support
catcher telephone number.
REQ/ACK. See request for acknowledgement and
acknowledgement.
request for acknowledgement and
acknowledgement (REQ/ACK). A cycle of
communication between two data transport devices for
the purpose of verifying the connection, which starts
with a request for acknowledgement from one of the
devices and ends with an acknowledgement from the
second device.
reserved allegiance. In Enterprise Systems
Architecture/390, a relationship that is created in a
control unit between a device and a channel path when
a Sense Reserve command is completed by the device.
The allegiance causes the control unit to guarantee
access (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.
R0. See track-descriptor record.
S
S/390 and zSeries. IBM enterprise servers based on
Enterprise Systems Architecture/390 (ESA/390) and
z/Architecture, respectively. “S/390” is a shortened form
of the original name “System/390”.
S/390 and zSeries storage. Storage arrays and
logical volumes that are defined in the ESS as
connected to S/390 and zSeries servers. This term is
synonymous with count-key-data (CKD) 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
a an I/O interface using the SCSI protocol. A SCSI
device is either an initiator or a target. See initiator and
Small Computer System Interface.
SCSI host systems. Host systems that are attached
to the ESS with a SCSI interface. Such host systems
run on UNIX, OS/400, Windows NT, Windows 2000, or
Novell NetWare operating systems.
SCSI ID. A unique identifier assigned to a SCSI device
that is used in protocols on the SCSI interface to
identify or select the device. The number of data bits on
the SCSI bus determines the number of available SCSI
IDs. A wide interface has 16 bits, with 16 possible IDs.
SCSI-FCP. Short for SCSI-to-fibre-channel protocol, a
protocol used to transport data between a SCSI adapter
on an open-systems host and a fibre-channel adapter
on an ESS. See fibre-channel protocol and Small
Computer System Interface.
Seascape architecture. A storage system architecture
developed by IBM for open-systems servers and S/390
and zSeries host systems. It provides storage solutions
that integrate software, storage management, and
technology for disk, tape, and optical storage.
serial connection. A method of device interconnection
for determining interrupt priority by connecting the
interrupt sources serially.
self-timed interface (STI). An interface that has one
or more conductors that transmit information serially
between two interconnected units without requiring any
clock signals to recover the data. The interface performs
clock recovery independently on each serial data stream
198 ESS Host Systems Attachment Guide
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