NonStop Systems Introduction

Glossary
NonStop Systems Introduction—527825-001
Glossary-9
requester-server model.
requester-server model. A model for application design that divides the tasks of data input,
data manipulation, and data output between two basic types of processes: requesters
and servers. A requester sends a request to a server. The server performs the
request and then replies to the requester. The requester and server can reside on the
same processor or on different processors in an Expand network. See also requester
and server.
response time. The amount of time it takes to receive a response from the system after
initiating a request message (for example, by pressing a function key).
ride-through power backup. The A battery-supported feature that permits a processor to
continue operation for a limited time (typically 20 or 30 seconds) when an AC power
outage occurs. If the power outage lasts longer than the ride-through time, a power-fail
interrupt occurs in order to preserve the current state of memory. See also power-fail
interrupt.
RISC. See reduced instruction-set computing (RISC).
router. See ServerNet router.
SAC. See ServerNet addressable controller (SAC).
SAN. See System area network (SAN)
scalability. The ability to increase the size and processing power of an online transaction
processing system by adding processors and devices to a system, systems to a
network, and so on, and to do so easily and transparently without bringing systems
down. Scalability is also sometimes called expandability. See also linear
expandability.
SCF. See Subsystem Control Facility (SCF).
server. (1) A process or program that provides services to a requester. Servers are
designed to receive request messages from requesters; perform the desired
operations, such as database inquiries or updates, security verifications, numerical
calculations, or data routing to other computer systems; and return reply messages to
the clients or requesters. A server process is a running instance of a server program.
(2) A combination of hardware and software designed to provide services in response
to requests received from clients across a network. For example, NonStop servers
provide transaction processing, database access, and other services.
server class. A set of duplicate copies of a single server process, all of which execute the
same object program. Server classes are configured through the PXMCFG utility.
ServerNet adapter. A customer-replaceable unit (CRU) that connects peripheral devices to
the rest of the system through a ServerNet bus interface (SBI).
ServerNet addressable controller (SAC). An input/output controller that is uniquely
addressable with a ServerNet node ID. A SAC is typically implemented on some