Sun Microsystems manual 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. Exclusive 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.

C-98	Sun Confidential: Internal Only	96257
	Revision A