Glossary g-47
Glossary
subnet mask A mask used by a computer to determine whether another computer
with which it needs to communicate is located on a local or remote
network. The network mask depends upon the class of networks to
which the computer is connecting. The mask indicates which digits to
look at in a longer network address and allows the router to avoid
handling the entire address. Subnet masking allows routers to move
the packets more quickly. Typically, a subnet may represent all the
machines at one geographic location, in one building, or on the same
local area network.
switch A device that connects, filters and forwards packets between local
area network (LAN) segments or storage area network (SAN) nodes
or devices.
switchover Changing a backup field-replaceable unit (FRU) to the active state,
and the active FRU to the backup state.
switch priority Value configured into each switch in a fabric that determines its rela-
tive likelihood of becoming the fabric’s principal switch. Lower val-
ues indicate higher likelihood of becoming the principal switch. A
value of 1 indicates the highest priority; 225 is the lowest priority. A
value of 225 indicates that the switch is not capable of acting as the
principal switch. The value 0 is illegal.
System Automation for
Operating System/390 SA OS/390™. IBM licensed software that provides System/390 Paral-
lel Sysplex™ management, automation capabilities, and integrated
systems and network management. SA OS/390 manages host, remote
processor, and I/O operations. SA OS/390 integrates the functions of
Automated Operations Control for Multiple Virtual Storage (MVS™),
ESCON™ Manager, and Target System Control Facility (D).
system name See product name.
system services
processor SSP. In a director or switch, the central controlling processor. Controls
the RS-232 maintenance port and the Ethernet port of a Fibre Channel
director or switch.
T
TB See terabyte.
TCP See transmission control protocol.