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track-descriptor record (R0). A special record on a
track that follows the home address. The control
program uses it to maintain certain information about
the track. The record has a count field with a key length
of zero, a data length of 8, and a record number of 0.
This record is sometimes referred to as R0.
transaction processing facility (TPF). A
high-availability, high-performance system, designed to
support real-time, transaction driven applications. The
specialized architecture of TPF is intended to optimize
system efficiency, reliability, and responsiveness for data
communication and database processing. TPF provides
real-time inquiry and update to a large, centralized
database, where message length is relatively short in
both directions, and response time is generally less than
three seconds. Formerly known as the Airline Control
Program/Transaction Processing Facility (ACP/TPF).
Transmission Control Protocol/Internet Protocol
(TCP/IP). (1) The Transmission Control Protocol and
the Internet Protocol, which together provide reliable
end-to-end connections between applications over
interconnected networks of different types. (2) The suite
of transport and application protocols that run over the
Internet Protocol.
transparency. See software transparency .
TSO. See time sharing option .
U
UFS. UNIX filing system.
Ultra-SCSI. An enhanced small computer system
interface.
unit address. The ESA/390 term for the address
associated with a device on a given controller. On
ESCON interfaces, the unit address is the same as the
device address. On OEMI interfaces, the unit address
specifies a controller and device pair on the interface.
Universaile Tempes du Coordinaire (UTC). The
basis for coordinated world wide time. This system,
formerly known as Greenwich Mean Time (GMT), was
officially renamed to UTC, for 'Universaile Tempes du
Coordinaire' because the world clock is now in Paris,
France. It is also known as coordinated universal time
(CUT).
UTC. See Universaile Tempes du Coordinaire .
utility device. The ESA/390 term for the device used
with the Extended Remote Copy facility to access
information that describes the modifications performed
on the primary copy.
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ESS Introduction and Planning
V
virtual machine (VM). A virtual data processing
machine that appears to be for the exclusive use of a
particular user, but whose functions are accomplished
by sharing the resources of a real data processing
system.
vital product data (VPD). Information that uniquely
defines the system, hardware, software, and microcode
elements of a processing system.
VM. See virtual machine .
volume. In the ESA/390 architecture, the information
recorded on a single unit of recording medium.
Indirectly, it can refer to the unit of recording medium
itself. On a nonremovable-medium storage device, the
terms may also refer, indirectly, to the storage device
that you associate with the volume. When you store
multiple volumes on a single storage medium
transparently to the program, you may refer to the
volumes as logical volumes.
VPD. See vital product data .
W
world-wide port name (WWPN). A unique 64-bit
identifier for a fibre-channel port that is assigned in an
implementation and protocol-independent manner.
write hit. A write operation in which the data that you
requested is in the cache.
write penalty. The performance impact of a classical
RAID write operation.
WWPN. See world-wide port name .
X
XRC. See Extended Remote Copy .
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