OSI/TS Configuration and Management Manual

Glossary
OSI/TS Configuration and Management Manual—424831-001
Glossary-4
Data chaining.
is part of the Dynamic System Configuration (DSC) facility, which is not used to
configure Compaq OSI subsystem objects, but which can be used to configure the
underlying X25AM and TLAM objects.
CSMA/CD (carrier sense multiple access with collision detection).
An IEEE 802.3 standard for the Physical Layer of the OSI Reference Model that
defines CSMA/CD data transmission over baseband or broadband LAN networks.
Data chaining. An addressing technique used in APS programming whereby the data
associated with a data-element header resides elsewhere in memory rather than in the
user data buffer and is pointed to by a field within the data-element header. This
technique, which is used only with the APS_DATA_REQ_ and
APS_TYPEDDATA_REQ_ procedures, enables the user to avoid moving large blocks
of data within memory.
Data Link Layer. Layer 2 in the OSI Reference Model. This layer packages data for
transmission across the network and ensures that the data arrives at the next layer
without any errors.
Data token. One of the four types of session -ayer tokens that are associated with functional
units. .
Data-transfer phase. The phase of an OSI connection in which data is transferred. This
phase begins when connection establishment is completed.
Dialog unit. In the Session Layer, the work carried out between two major synchronization
points chosen by the application.
Distributed Systems Management. See DSM (Distributed Systems Management).
Distributor. An EMS process that distributes event messages from event logs to requesting
management applications, to console message destinations, or to a collector on another
node.
DNS (Distributed Name Service). A part of DSM used to simplify the management of
objects in a NonStop system or an Expand network by managing a distributed, and
partially replicated, database of objects. DNS has both a programmatic and an
interactive interface.
DSC (Dynamic System Configuration). A facility that allows system managers to make
online changes to the configuration of devices and controllers. Its interactive utility
program is called the Configuration Utility Program (COUP). DSC is not used to
configure Compaq OSI subsystem objects, but can be used to configure the underlying
X25AM and TLAM objects.
DSM (Distributed Systems Management). A set of tools used to manage NonStop systems
and Expand networks. These tools include the Viewpoint console application, the
Subsystem Control Facility (SCF) for data communications subsystems, the Subsystem
Programmatic Interface (SPI), the Event Management Service (EMS), the Distributed