IBM SAN32M1, Installation And Service Manual

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SAN32M1 Fabric Switch Installation and Service Manual 576
mers. UNIX was one of the first operating systems to be written in a
high-level programming language, namely C. This meant that it
could be installed on virtually any computer for which a C compiler
existed. Due to its portability, flexibility, and power, UNIX has
become the leading operating system for workstations. Historically, it
has been less popular in the personal computer market, but the emer-
gence of a new version called Linux is revitalizing UNIX across all
platforms.
upper level protocol ULP. Protocols that map to and run on top of the Fibre Channel FC-4
layer. ULPs include Internet protocol (IP) and small computer system
interface (SCSI).
UPS
See uninterruptable power supply .
user datagram
protocol
UDP. A connectionless protocol that runs on top of Internet protocol
(IP) networks. User datagram protocol/Internet protocol (UDP/IP)
offers very few error recovery services, instead providing a direct
way to send and receive datagrams over an IP network. UDP/IP is
primarily used for broadcasting messages over an entire network.
Contrast with
transmission control protocol/Internet protocol .
V
VAC
See volts alternating current .
VDC
See volts direct current .
virtual machine VM®. (1) A virtual data processing system that appears to be at the
exclusive disposal of a single user, but whose functions are accom-
plished by sharing the resources of a real data processing system. (2)
A functional simulation of a computer system and its associated
devices, multiples of which can be controlled concurrently by one
operating system (D, T).
virtual storage VS. (1) Storage space that may be regarded as addressable main stor-
age by the user of a computer system in which virtual addresses are
mapped to real addresses. The size of virtual storage is limited by the
addressing scheme of the computer system and by the amount of
auxiliary storage available, not by the number of main storage loca-
tions. (2) Addressable space that is apparent to the user as processor