unit address
For System z, the address associated with
a device on a given control unit. On
ESCON interfaces, the unit address is the
same as the device address. On OEMI
interfaces, the unit address specifies a
control unit and device pair on the
interface.
unprotected volume
An AS/400 term that indicates that the
AS/400 host recognizes the volume as an
unprotected device, even though the
storage resides on a RAID-formatted
array and is, therefore, fault tolerant by
definition. The data in an unprotected
volume can be mirrored. Also referred to
as an unprotected device.
upper-layer protocol
The layer of the Internet Protocol (IP) that
supports one or more logical protocols
(for example, a SCSI-command protocol
and an ESA/390 command protocol).
Refer to ANSI X3.230-199x.
UTC See Coordinated Universal Time.
V
virtual machine facility
A virtual data processing machine that
appears to the user to be for the exclusive
use of that user, but whose functions are
accomplished by sharing the resources of
a shared data processing system. An
alternate name for the VM/370 IBM
operating system.
vital product data (VPD)
Information that uniquely defines the
system, hardware, software, and
microcode elements of a processing
system.
VM The root name of several IBM operating
systems, such as VM/XA, VM/ESA
®
,
VM/CMS, and z/VM. See also virtual
machine facility.
volume
For System z, 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
term can also indirectly refer to the
storage device associated with the
volume. When multiple volumes are
stored on a single storage medium
transparently to the program, the volumes
can be referred to as logical volumes.
volume group
A collection of either physical or logical
volumes.
volume label
A unique identifier that a user assigns to
a logical volume.
VPD See vital product data.
VSE/ESA
An IBM operating system, the letters of
which represent virtual storage
extended/enterprise systems architecture.
W
weight distribution area
The area that is required to distribute the
weight of the storage unit.
worldwide node name (WWNN)
A unique 64-bit identifier for a host that
contains a fibre-channel port. See also
worldwide port name.
worldwide port name (WWPN)
A unique 64-bit identifier associated with
a fibre-channel adapter port. It is assigned
in an implementation- and
protocol-independent manner. See also
worldwide node name
write hit
A write operation in which the requested
data is in the cache.
write penalty
The performance impact of a classical
RAID-5 write operation.
WWNN
See worldwide node name.
WWPN
See worldwide port name.
Z
z/Architecture
An IBM architecture for mainframe
computers and peripherals. The System z
family of products uses the
z/Architecture architecture. It is the
successor to the S/390 and 9672 family of
servers. See also System z.
212 DS8000 User’s Guide
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