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C-98 Sun Confidential: Internal Only 96257
Revision A
VTCS. Virtual Tape Control System. In VSM, primary
host software that controls activity and coordinates oper-
ations between the host operating system and the
VTSSs, VTVs, RTDs, and MVCs, as represented in
front-end tape drives or libraries and back-end disk ar-
rays. VTCS software operates in the same address
space as the HSC, and communicates closely with it.
VTD. Virtual Tape Drive. A transport in a VTSS that emu-
lates a physical 3490E tape drive to a MVS system. The
data written to a VTD is really being written to the disk
buffer (VTSS). A VTSS has 64 VTDs that do virtual
mounts of VTVs.
VTSS. Virtual Tape Storage Subsystem. In VSM, a back-
end disk array storage device (buffer) containing virtual
tape volumes and transports. VTSS is a RAID 6+ hard-
ware device with microcode that enables emulation of
256 transports. The RAID device can read and write
‘tape’ data from/to disk, and can read and write the data
from/to an RTD. Using data compression algorithms and
other proprietary techniques, a VTSS presents its physi-
cal storage capacity as a much larger pool of ‘virtual’ ca-
pacity (typically, a 4:1 ratio) to a tape storage device or
host.
volatile memory. A repository that does not retain data
when AC power is turned off. In VTSS, volatile memory
temporarily stores data being sent from back-end disk
arrays to a host. Contrast with nonvolatile storage
.
VOLSER. VOLume SERial (number). A six-character al-
phanumeric name that identifies a disk volume to a host
system.
volume. See functional volume
.
VTOC. Volume table of contents. A table on a disk vol-
ume that describes each data set on the volume.
VTV. Virtual Tape Volume. A ‘tape cartridge’ image
whose volume number is known to an MVS catalog and
TMS (Tape Management System) as a tape data set.
W
warm boot. Also called warm start. The act of restarting
a computer, storage system, etc. Without turning the
power off. Contrast with cold boot.
work mat. A nonpermanent, removable island of materi-
al, typically made of conductive or dissipative layers or
composite materials, which is placed over a floor to drain
static charges that are generated by groundable person-
nel or objects. See also wrist strap.
wrist strap. A device consisting of a grounding cord and
conductive band that connects to a grounding outlet on a
machine and makes electrical contact with the wearer’s
skin to drain static charges from the wearer to earth
ground. See also work mat
.
write. To make record data permanently or transitorily in
a storage device or on a data medium.
write hit. An instance where data to be updated by a
write operation is in cache. Contrast with read hit
.
write miss. An instance where data to be updated by a
write operation is not in cache. Contrast with read miss
.
write operation. An output operation that sends a pro-
cessed record to an output device or output file.
write-protect tab. A sliding device placed over a write-
protect notch on a floppy disk to prevent recording of da-
ta over existing pre-recorded data on the disk.
WWTS. Worldwide Technical Support.
X
x-axis. The horizontal axis, representing width, in a two-
dimensional (x-y) or three-dimensional (x-y-z) coordinate
system. Contrast with y-axis, z-axis.
XOR. Ex
clusive OR. A method used to calculate parity
information in RAID configurations.
XSA. Extended Storage Architecture.
Y
y-axis. The vertical axis, representing height, in a two-di-
mensional (x-y) or three-dimensional (x-y-z) coordinate
system. Contrast with x-axis, z-axis.
Z
z-axis. The third dimension, representing depth, in a
three-dimensional (x-y-z) coordinate system. Contrast
with x-axis, y-axis.