Tape Coordinator

DFS: A process that runs on a Tape Coordinator machine and controls the behavior of one tape drive. There must be one Tape Coordinator running for each tape drive in use.

Tape Coordinator ID (TCID)

DFS: A number, assigned when a Tape Coordinator machine is configured, that uniquely identifies each Tape Coordinator and the associated tape drive. Backup operators use it to specify the Tape Coordinator that is to execute a command.

Tape Coordinator machine

DFS: A client machine on which backup and restore operations are performed with the DFS Backup System. Each Tape Coordinator machine must have one tape drive attached and must run one instance of the butc process for each drive.

target restrictions

Restrictions on the targets to whom a client's delegated identity can be projected.


See Tape Coordinator ID.


See Transmission Control Protocol.


See Time Differential Factor.


A single sequential flow of control within a process.

thread handle

RPC: A data item that enables threads to share a memory management environment.

thread-serial service

A reentrant system service is thread-serial if it blocks the current thread and all other threads that attempt to call the same service or other related services until the first call returns.

thread-synchronous service

A reentrant system service is thread-synchronous if it blocks only the current thread and allows other threads to execute the same operation during the block.


DTS: The clock timer interrupt that causes the operating system to increment the system time.


An application-transparent mechanism that transmits the identity of an initiating principal to its target. A simple ticket contains the principal's identity, a session key, a timestamp, and other information, sealed using the target's secret key. A privilege ticket contains the same information as a simple ticket, and also includes a privilege attribute certificate. A ticket- granting ticket is ticket to the ticket-granting service; a service ticket is a ticket for a specified service other than the ticket-granting service.

Time Differential Factor (TDF)

DTS: The difference between UTC and the time in a particular time zone.

time provider

DTS: A hardware device that monitors UTC time and forwards it to a DTS server.

Time Provider Interface (TPI)

A software intermediary between the DTS server and external time provider processes. The DTS server uses the interface to obtain UTC time values and to determine the associated inaccuracy of each value.

time provider program

DTS: Software that enables a time provider device to call the time provider interface and supply time values to a DTS server.


A mechanism by which running threads are preempted at fixed intervals. This ensures that every thread is allowed time to execute.


DFS: A device sent along with requested data from a File Server machine to a client machine to indicate the types of operations (for example, read or write) the client can perform on the data. It prevents simultaneous access while permitting cooperative access; for example, only one client can possess a write token for a single piece of data at any given time. A client must have the appropriate tokens to operate on a File Exporter. See also data token.

token management layer

DFS: The part of the DFS Cache Manager that handles file and directory tokens. See also Token Manager.

Token Manager

DFS: A component that maintains the set of file and directory tokens that have been granted to existing clients of a File Server machine. See also token management layer.

top-level pointer

RPC: A pointer parameter that, in a chain of pointers, is the only member that is not the referent of any other pointer.


Physical address and protocol information for a particular server. CDS uses this information to locate the system on which a server resides and to determine which protocols are available at the server. Tower values are contained in the CDS_Towers attribute associated with the object entry that represents the server in the cell namespace.

TP server

DTS: A server system connected to a time provider.


See Time Provider Interface.

traced delegation

Transmission of a delegation initiator's identity in a manner that preserves the identities of each participant in a call chain.


A related set or unit of changes to metadata. The events in a transaction are atomic. No change takes effect unless all the changes that make up that transaction are performed. See also log.

transfer syntax

RPC: A set of encoding rules used for transmitting data over a network and for converting application data to and from different local data representations. See also Network Data Representation.

Transmission Control Protocol (TCP)

A protocol of the Internet Protocol (IP) family.

transmitted type

RPC: For data types with the IDL transmit_as attribute, the data type that stubs pass over the network. Stubs invoke conversion routines to convert the transmitted type to a presented type, which is manipulated by clients and servers. See also presented type.

transparent access

DFS: A feature that allows users to access files without needing to know which machine stores the files. The FLDB keeps track of fileset locations, so the user needs to know only a file's path name. See also Fileset Location Database.

transport independence

RPC: The capability, without changing application code, to use any transport protocol that both the client and server systems support, while guaranteeing the same call semantics. See also transport layer, transport protocol.

transport layer

A network service that provides end-to-end communications between two parties, while hiding the details of the communications network. The TCP and ISO TP4 transport protocols provide full-duplex virtual circuits on which delivery is reliable, error free, sequenced, and duplicate free. UDP provides no guarantees (the connectionless RPC protocol provides some guarantees on top of UDP).

transport protocol

A communications protocol from the transport layer of the OSI network architecture, such as the TCP or the UDP.


A remote operation, associated with an attribute type, that is executed when attributes of that type are either queried or updated.

trigger type

A classification, either query or update, on a trigger that identifies on which attribute operation the trigger will be invoked.

trust path

See authentication path.

trust peer

A characterization of one cell with respect to another with which the cell maintains a mutual authentication surrogate.


XOM: A category into which attribute values are placed on the basis of their purpose. See also attribute type.

type UUID

RPC: The universal unique identifier that identifies a particular type of object and an associated manager. See also manager, object, Universal Unique Identifier.