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Glossary
OSI/FTAM Responder Manual—425199-001
Glossary-17
OSI Reference Model. A communications architecture, adopted by the ISO in 1984,
that includes seven layers that define the functions involved in communications between
two systems, the services required to perform these functions, and the protocols
associated with these services. See also layer.
OSI subsystems. The Compaq subsystems that support the various layers and
application service elements of the OSI Reference Model, including the FTAM
subsystem, APLMGR, OSI/AS, OSI/TS, and TLAM or X25AM.
OSI/TS (Transport Services). The Compaq subsystem that manages the
communication of messages from the Transport Layer on a local Compaq system to the
Transport Layer on a remote system in an OSI network.
owner ID. The identity (Guardian user ID) of the owner of a process on a Compaq
NonStop system.
parallel associations. Multiple associations running concurrently within a Compaq
FTAM process.
parameter structures. DDL structures that define some of the reference parameters for
the FTM, APS, and MFM procedures.
partially supported file attribute. A virtual filestore (VFS) file attribute, in a supported
storage or security attribute group, for which any reference by the FTAM responder
yields the result that no value is available, and any attempt to change the attribute fails.
In summary, the VFS recognizes the attribute name but provides no value for it.
Contrast with supported file attribute.
PDU (protocol data unit). The encoded message transferred across the OSI network
between peer entities—for example, between an FTAM initiator and responder. Data,
such as a block of information being transferred or a protocol primitive, is encoded into
a PDU for transfer across the network. The PDU is decoded when it arrives at its
destination. Types of PDUs include the following:
•
APDU (application PDU): information exchanged between Application Layer
entities—this includes ACSE and presentation PDUs created to support the FTAM
protocol (FTAM PDUs, or FPDUs)
•
PPDU (presentation PDU): information exchanged between Presentation Layer
entities
•
SPDU (session PDU): information exchanged between Session Layer entities
•
TPDU (transport PDU): information exchanged between Transport Layer entities
permanent error. An ISO-defined type of diagnostic error that occurs every time the
sequence of events that caused the error is repeated, and implies the failure of at least the
present operation being performed. See also error type, informative message, and
transient error.
permitted-actions attribute. A file attribute that can be returned in an F-READ-
ATTRIB indication or confirm or set in an F-CREATE request. It specifies the actions
that can be performed on the file or the mode of access to FADUs in the file. During the
F-CREATE service, the initiator proposes a set of values. The responder can either
accept the proposed values or change them to any set of values it can handle: for