Glossary

Glossary

A

abstract class
An abstract class is one that contains pure virtual functions that must be defined by any class that is derived from it. An abstract class has no instances other than instances of its derived classes. A method defined by an abstract class is called an abstract method if derived classes must override the method to perform real work.

adapter activator
A server-side object used by the ORB when a request is made for a child POA that does not exist. In such a case, the adapter activator creates the child POA.

architecture
The view of a system that focuses on functional components and their relationships.

attribute
An identifiable association between an object and a value. An attribute A is made visible to clients as a pair of operations: get_A and set_A. Read-only attributes generate only get operations. An attribute is a characteristic or property of an object and it is typically implemented as a simple data member or as an association with another object or group of objects.

availability
Continuous service. Tandem NonStop systems are designed to provide high availability.

AWAITIO(X)
A Guardian file-system call that permits the caller to retrieve the reply to a no-waited request. A NonStop DOM application component must not use this call with -1 as the file number.

B

base class
A class from which some other class (a subclass) is derived, so that the subclass inherits characteristics from the base class and also defines characteristics of its own.

base client, listener, or server event handler or user
The abstract class in NSDEvent from which a protocol-specific event handler or user object class is derived.

Basic Object Adapter (BOA)
See object adapter.

binding
In IDL, the relationship between an IDL construct and the corresponding construct in a programming language. There are two types of bindings: usage bindings for use by clients, and implementation bindings for use in object implementations.

In the Naming Service, the relationship between a name and the object it represents.

In networking, binding is the establishment of a logical connection between communicating entities.

block
To prevent another requester from gaining access to a resource, as in "the second request is blocked until after the first has been completed."

C

cast
To assign a value of one type to a variable of another type.

child class
An object class that inherits characteristics from another class.

class data
Variables that apply, not to a specific object instance, but to an object class as a whole; for example, a variable that reports the number of instances of a class.

class library
A set of related object classes. A user creates and makes requests of objects defined by a class library.

CLI
See Command Line Interface.

client
In object technology, an application component that makes requests of an object. More generally, an application component that makes requests of a server.

client event handler
An object that supports asynchronous communication for an NSDEVENT, NonStop DOM clients, and server wrappers.

client/server computing
A style of application in which function is divided between a client, which makes requests on behalf of a user, and a server, which executes those requests. In many cases, the client runs on a workstation and the server runs on a larger server machine, but this pattern of distribution is not a necessary characteristic of client/server computing.

collection classes
A set of classes that define containers for other objects. For example, you use collection classes to form queues, stacks, linked lists, and dictionaries.

Comm Server
A NonStop DOM process that manages the linkage between remote clients and local servers. There can be multiple Comm Servers in a configuration, and many clients can use the same Comm Server.

Command Line Interface (CLI)
The method for accepting input lines from either stdlin or a script file. On Open System Services, this would be a primitive command line interface.

commit
Declare (a transaction) complete.

Common Object Request Broker Architecture (CORBA)
A definition of standard components and required interfaces to support the interaction of object-oriented components across heterogeneous networks. CORBA is defined by the Object Management Group (OMG).

CORBA object
A CORBA object is derived from the base class CORBA::Object. An ORB object that receives client requests. This is the target for all client invocations. The CORBA object is locatable by its reference. Exactly how the CORBA object satisfies a request is transparent to the client.

Common Object Services (COS)
A series of OMG specifications for services useful to applications in the context of CORBA. COS includes a lifecycle service, a persistence service, an event service, and a Naming Service, among others. Also called CORBAServices.

component
A discrete unit of application function-such as a client, server, or class library, typically suitable for mixing and matching with other components to create one or more different applications. (One goal of component-based application development is to use the same component in different applications.)

concurrency
Simultaneous operation. This term can apply to processes running in parallel, simultaneous transactions, multiple instances of a class in the same process, or multiple clients using the same object (or other resource) at the same time.

concurrency service
An application service that manages simultaneous access to objects by multiple clients, primarily by supporting read and write locking requests.

constructor
A method that creates an instance of the object class in which the method is defined.

control object
A type of object whose purpose is to coordinate other objects, for example, to perform transactions on a set of objects that represent stored data.

CORBA
See Common Object Request Broker Architecture.

CORBAServices
See Common Object Services.

COS
See Common Object Services.

CSMAP
The NonStop DOM database whose entries determine which Comm Server each configured client will use. Entities in the configuration database that hold CS load mappings between remote clients and client/servers.

Current interface
An object class, defined by the Object Transaction Service (OTS), which gives the OTS client control over application transactions. For example, the Current interface defines methods to mark the beginning of a transaction, to commit a transaction, to suspend a transaction, and to undo (roll back) a transaction.

D

database mapping
See mapping.

data type
A categorization of values, operations, and arguments that usually cover both behavior and representation.

deprecated
Possibly available as a feature for upward compatibility of existing applications, but not recommended for use by new applications.

derived class
An object class that inherits characteristics from another class.

destructor
A method that is used to destroy an object and usually releases memory allocated to the object or otherwise clears the initiated action.

dictionary
An indexed collection of information, defined as a collection class in RogueWave's Standard Template Library (STL).

Distributed Computing Environment (DCE)
A set of application services defined by the Open Software Foundation (OSF) and suitable for distributed applications. DCE includes a time service, cell and global directory services, a threads package, and a file service (among others). NonStop DCE is a Tandem product that implements some but not all features of OSF DCE.

distributed object computing
A style of application in which object-based components distributed across processes or a network communicate using a message-based interface.

dynamic context
Information that must be retained in the memory of a process, as opposed to being saved on disk, between method calls.

Dynamic Invocation Interface (DII)
A request style in which the client constructs a request at runtime, not needing to know the object interface (the calling sequences for requesting specific operations) at compile time.

dynamic link library (DLL)
A way of packaging application functions that lets the functions be loaded into a process at runtime rather than compile time. Such functions can be unloaded when they are no longer required in the application while the rest of the application continues to run.

E

encapsulation
The characteristic of object technology that protects the data space of the server from direct access by the client and ensures that the client can invoke only functions defined for the data.

Enscribe
The Tandem NonStop kernel disk process and related interfaces.

entity object
A type of object that represents external data, such as a database record, or possibly an external device.

environment parameter
A CORBA-defined variable included in method invocations to receive exception information.

environment structure
A CORBA-defined variable included in method invocations to receive exception information.

environment variable
An element of a system or product-specific configuration file, used to specify the path to a processing component or to control some aspect of system or product operation. For example, you use an environment variable in the OSS profile file to specify the location of the NonStop DOM configuration file.

event
In NonStop DOM, an asynchronous message sent by one object to another. In Tandem Distributed System Management (DSM), an error or other occurrence of significance to the operator, described in a message from a software subsystem to the Tandem Event Management Service (EMS).

event handler
A NonStop DOM object that supports asynchronous communication between a NSDEVENT application process and other processes, for example, a legacy client or server. Event handlers are specialized to manage connections using file-system, context-sensitive Pathway, or TCP/IP protocol.

event handler user
An object that controls an event handler on behalf of an application process.

Event Management Service (EMS)
A set of processes and interfaces through which Tandem products report significant events to a common location, for subsequent distribution to operators and management applications. EMS supports filters through which the user can request messages from specific products or messages having specific content or characteristics.

event service
A standard application service (one of the OMG Common Object Services) for asynchronous communication among objects.

exception
An unacceptable condition that arises during the operation of a program that must be caught by exception handling code. Most exceptions are error conditions, but the exception mechanism can also be used to note other kinds of occurrences.

externalization service
A standard application service (one of the OMG Common Object Services) that supports the movement of object state information from one process or medium to another, using the abstract concept of a "stream." The sender performs any transformations required to write the data to the stream; the receiver performs transformations required to process the data in its local environment.

F

factory object
An object whose purpose is to create other objects. The Naming Service includes a factory service to permit registration of factory objects.

file system
An interface, provided with the Tandem NonStop kernel, that provides high-level communication between processes or between a process and an external device.

fleshed-out script
The results of editing skeletons, for example, nsdstart or default.db. Once configured, the fleshed-out script can be used to start, stop, or uninstall an existing NonStop DOM installation.

framework
A set of related object classes, technically different from a class library in that the framework makes requests of a user program. However, many software vendors use the terms "class library" and "framework" interchangeably.

G

gateway
A process or other component that provides a translation function between otherwise incompatible components.

granularity
The complexity of an object, whether it consists of few or many discrete operations or data items.

H

header file
A source file that is included in a C or C++ program to make available a set of data definitions or services.

host
Provide execution space for an object. A server can host instances of one or more object classes.

HOSTS file
A file that contains IP addresses and aliases representing systems known to NonStop TCP/IP.

I

identifier
An identifier is a sequence of alphabetic (a-z, A-Z) and numeric (0-9) characters. Identifiers can include the underscore. Identifiers must start with an alphabetic character, be case sensitive, and can be any length.

IDL compiler
See Interface Definition Language (IDL).

IDL specification
The series of IDL statements that define the interface of a particular object class. See also Interface Definition Language (IDL).

IIOP
Internet interORB protocol.

implementation
The data definitions and methods of an object class. A programmer produces the implementation from a skeleton emitted by the IDL compiler.

implementation binding
See binding.

implementation language
The programming language used to create the source code for an object class.

Implementation Repository
A database that records information about objects implementations and the servers in which they can reside.

inheritance
The propagation of characteristics from a base (or parent) class to a subclass. More generally, the propagation of a characteristic from a data type to a subtype.

install host
The system, in a network of systems, on which you first install NonStop DOM, and which holds the highest-level entry in the distributed Naming Service.

instance
A specific object conforming to the definition of an object class, containing data of the types and supporting the operations defined for the class. For example, an object that represents a particular person's bank account is an instance of the object class that generically defines bank accounts.

interface
The data attributes and calling sequences for methods that an object class makes accessible to clients. (An object class can also define private variables and functions.)

Interface Definition Language (IDL)
A language specified by OMG, used to define the inheritance relationships, data, and method signatures of object classes. IDL is independent of the languages used to implement objects; the IDL compiler produces language-specific header files according to CORBA-defined mappings between IDL and supported implementation languages.

interface object
An object whose purpose is to communicate with the user or device that originates requests in an application. This term is used in one popular object-oriented design methodology (Jacobson).

IP address
The style of network address associated with the TCP/IP protocol.

IPC
Interprocess communication. Tandem NonStop systems use a message-based style of IPC.

Interface Repository (IR)
A database containing information about object interfaces: the data accessible through an object and the calling sequence for each operation the object supports. The term used in object technology to mean a calling sequence is "method signature."

The component of the Object Request Broker that provides persistent storage of the IR definition. The IR definitions are maintained in the Interface Repository as a set of IR definition objects.

Internet InterORB Protocol (IIOP)
See InterOrb Protocols (IOPs).

interoperability, interoperation
The ability of heterogeneous hardware or software components to work together, especially across a network.

InterOrb Protocols (IOPs)
Rules for transmitting messages among distributed systems. CORBA defines the Internet InterORB Protocol (IIOP), which uses TCP/IP.

IR
See Interface Repository (IR).

IR browser
An interactive utility that provides a diagrammatic representation of the interface repository.

irdump utility
A program provided with NonStop DOM, which lists the contents of the interface repository.

K

key
A variable that provides an index into a dictionary. See also dictionary.

L

language binding or mapping
See binding.

language independence
The characteristic that permits a client to use an object written in another language, and that permits a subclass to be derived from a parent class written in another language.

Legacy client
A non-CORBA client.

Legacy client wrapper
A NonStop DOM application that acts as a legacy server, transforming legacy system requests into CORBA method invocations, and CORBA method completions into legacy system replies.

legacy server
A non-CORBA server.

Legacy server wrapper
A NonStop DOM application that acts as a server, transforming CORBA method invocations into legacy server requests, and replies to CORBA method invocations.

legacy system
For NonStop DOM, an existing system that is not based on the CORBA model.

lifecycle
The series of steps through which an object is created and deleted, activated and deactivated.

lifecycle service
A standard application service for creating and deleting objects. See also Common Object Services (COS).

link
A logical connection between processes. In NonStop TS/MP, the logical connection between a requesting process and a server in a server pool.

LINKMON process
The NonStop TS/MP process that obtains links for all requesters in a CPU.

listener event handler
An NSDEVENT object that waits for connection indications between a NonStop DOM server and a client, for example, NonStop DOM client, non-CORBA client. See also server event handler.

literal
A value that identifies an entity that is not an object.

Literals can be categorized as follows:

load balancing
The distribution of network traffic or application workload across available lines or processes, respectively.

local/remote transparency
The characteristic that makes it unnecessary for a client to know whether an object it uses is local or remote.

Location Service Daemon (LSD)
A NonStop DOM process that assigns a client to a Comm Server and looks up the addresses of direct TCP servers with persistent policy. See also Comm Server.

M

Makefile
A file that describes the dependencies among application modules that together constitute an executable program. The make utility (present in Tandem OSS and other implementations of UNIX or POSIX) interprets a makefile and initiates recompilation of changed and dependent modules.

mapping
The relationship between an IDL construct and the corresponding construct in a programming language, or the relationship between the data in an object instance and the corresponding entry in a database.

marshaling
The packaging of a request for transmission to a remote object, or of a response for transmission to a remote client. This is a function provided by an Object Request Broker. The term "demarshalling" refers to the processing of incoming messages for delivery to local objects and clients.

message
In general object technology, information passed from one object to another: a method invocation results in a message to the target object, and the reply results in a message from the target object to the client. Physical movement of data does not necessarily occur.

In NonStop DOM, a body of data intended for interprocess transfer by an event handler. A message object consists of a list of pointers to message data (MD) segments, which contain the actual data. The NonStop DOM message object includes methods that applications can use to manipulate a message.

message data (MD) segment
A logical subdivision of a message. a NonStop DOM message object creates segments automatically as the application writes to a message. Alternatively, the application can explicitly create and operate on message data segments.

message factory
a NonStop DOM object class that applications use to create and free messages and message data segments.

method
An operation defined for an object, implemented as a procedure or function in a programming language. The calling sequence for a method is called a method signature. A call to a method is called a method invocation.

MP (Massively Parallel)
A suffix included in the names of many Tandem products to signify their scalability.

multi-tiered architecture
See tiered application architecture.

N

name binding
Also known as name-object binding. An object consisting of a name and a binding.

name component
A structure containing a name-id string and a name-kind string.

naming context
An object that contains a set of name bindings in which each name is unique. To resolve a name is to determine the object associated with the name in a given context.

Naming Service
A standard application service (one of the OMG Common Object Services) for storing object names, identifiers, and possibly other information. One important use of the Naming Service is to store the names of factory objects to use in creating other objects.

narrowing
A term used in CORBA when moving from a base interface to a derived interface. C++ refers to this as down-cast.

nested transactions
Transactions that begin and end within another transaction.

NonStop Distributed Object Manager/Massively Parallel (NonStop DOM)
A set of products that let you develop object-oriented applications and components for Tandem systems, NonStop DOM is based on the CORBA standards of the Object Management Group (OMG). It includes both a development environment and a runtime environment.

NonStop DOM
See NonStop Distributed Object Manager/Massively Parallel.

NonStop TCP/IP
The Tandem product that implements the TCP/IP protocol. NonStop DOM uses NonStop TCP/IP for communication with remote clients and servers.

NonStop Transaction Manager/Massively Parallel (NonStop TM/MP)
A Tandem product that protects database consistency by allowing applications to undo failed transactions, and by providing for database recovery after a catastrophic failure.

NonStop Transaction Services/Massively Parallel (NonStop TS/MP)
A transaction processing (TP) monitor for Tandem systems. NonStop TS/MP manages server pools by establishing links between clients and servers, balancing the workload across servers, automatically creating and deleting servers in response to changes in request traffic, and restarting servers after CPU or process failures.

O

object
An instance of an object class. Some books also use the term "object" to mean object class.

object adapter
A CORBA component, residing in a server, which provides an interface between the Object Request Broker and the objects running in a server. CORBA defines a Portable Object Adapter (POA).

object class
An application component that defines a collection of data and the operations that can be performed on the data. An object, consisting of specific data and supporting the set of operations, is an instance of the object class.

object ID
A value used to identify a CORBA object. The value is unique only within a POA scope. An object ID is not guaranteed to be unique with respect to a server since there could be more than one POA object at any time on a given server. An object ID is opaque and is not visible to the client.

object identity service
A service that distinguishes among instances of the same object class, even in cases where the data values are identical.

Object Management Group (OMG)
The vendor consortium responsible for defining the Common Object Request Broker Architecture (CORBA).

object-oriented
Characteristic of an application in which function is partitioned into small modules that encompass data and the actions to be performed the data.

object reference
A value that precisely identifies an object. Object references are never reused to identify another object.

Object Request Broker (ORB)
A component that transmits messages between clients and servers in a distributed object environment. The ORB provides services such as locating the target object and performing any transformations required for transmission of a request or receipt of a response across the network. See also marshaling.

object services
See Common Object Services.

Object Transaction Service (OTS)
See transaction service.

object wrapper
The result of encapsulating services from a non-CORBA (or legacy) application or program interface to treat the encapsulated application or interface as an object. See also wrapping.

OMG
See Object Management Group.

Open System Services (OSS)
A set of POSIX-compliant operating system interfaces for the Tandem NonStop Kernel.

operator
A language symbol that represents an arithmetic or logical operation or relationship.

ORB
See Object Request Broker.

osh
The utility through which you invoke any other utility in the Open System Services (OSS) environment. In UNIX terminology, this type of utility is called a shell. The Guardian interface that offers similar features is TACL.

OSS
See Open System Services.

OTS
See transaction service.

overloading
The redefinition of a language element to provide for different behavior depending on context. For example, the addition operator (+) could be overloaded to support concatenation of text strings.

overriding
Replacing a data element or method in a base class with another data element or method having the same name. For example, if the base class defines a method called report, which produces a report in a specific format, a subclass can override (redefine) that method so a "report" request to an object of the subclass will produce a report in a different format.

P

parallelism
A means of improving performance and potentially fault-tolerance by allowing multiple processing tasks to proceed simultaneously. Threads and server pools are two mechanisms for achieving parallelism.

parent class
A class from which some other class (a subclass) is derived, so that the subclass inherits characteristics from the parent class and also defines characteristics of its own.

partitioning
The distribution of data across files and storage media, the distribution of application logic across processes, or the distribution of objects among server processes.

PATHCOM
The CLI utility used to define and manage TS/MP server pools and other components of NonStop TS/MP.

PATHCOM configuration file
A file that defines processes and operational parameters for a PATHMON environment (the set of processes under control of a single PATHMON process).

PATHMON
The NonStop TS/MP process responsible for starting, restarting, and monitoring server processes, establishing links between requesters and servers, and load balancing. The set of processes managed by an instance of PATHMON is called a PATHMON environment.

Pathsend facility
The set of procedures a requester uses to exchange requests and replies with a NonStop TS/MP server pool. (The actual procedure call to send a messages can have a different name, such as SERVERCLASS_SEND.) NonStop DOM uses the Pathsend facility internally to support invocations of objects running in NonStop TS/MP server pools. A client program can also use the facility explicitly to send a non-CORBA message to a server pool that is not CORBA compliant.

Pathway protocol
The mechanism NonStop DOM uses to allow communication between a client and a NonStop TS/MP server pool. This protocol uses the NonStop TS/MP Pathsend facility.

pax
A utility for extracting a set of files that have been archived as a single file. pax is available on UNIX and POSIX systems, including Tandem systems using Open Systems Services (OSS).

persistent identifier (PID)
A value used to relate an object to the external entity (for instance, a database record) that the object represents.

POA
See Portable Object Adapter (POA).

POA manager
A server-side object that contains the processing state for one or more POAs. Developers can use the POA manager to process, queue, or discard requests. The manager can also activate or deactivate POAs.

polymorphism
The characteristic of object technology that allows a client to make the same request of different objects and assume that the operation will be performed appropriately for each class of object. For example, a display operation on a video object does not result in the same behavior as a display operation on a text file; the client treats them both the same.

port number
An addressing component used to associate multiple local destinations with a single network (IP) address. For example, a TCP/IP process listens on one IP address but can route requests to different local processes based on port number.

Portable Object Adapter (POA)
The CORBA-specified object adapter (replaces earlier CORBA BOA) that connects an object residing on a server with an ORB. The adapter provides a name space within which the client and the server can connect and exchange information. See also object adapter.

policy
A policy specifies a POA characteristic behavior for objects implemented in that particular POA. For example, a policy can determine threading, activation, object id assignment, and so on. Every POA has default policies if no other one is specified.

porting
Rewriting or modifying an existing component to run on a different system or platform.

POSIX
A standard set of operating system interfaces similar to UNIX. The Tandem Open System Services (OSS) product provides POSIX interfaces to the Tandem NonStop kernel.

profile file
The configuration file that defines the operational parameters for Open System Services (OSS).

proxy
A local reference to a remote object, used in such a way that an operation invoked on the proxy is performed on the remote object.

Ptrace
A utility program that produces a formatted display of SCF trace information.

Q

QIO
A Tandem product that uses shared memory segments to optimize the performance of its client process. One Tandem product that uses QIO is the Tandem LAN Access Method (TLAM). QIO stands for Queued Input/Output.

R

receiver
A pointer to the object that is the target of a method invocation.

reuse
The principle of using a software component in multiple applications, for example by deriving application-specific object classes from general-purpose object classes, or using existing class libraries or frameworks for common application functions. Reuse is one of the goals of object technology.

roll back
Undo (a transaction).

Root POA
The POA object provided by the ORB to which all other POA objects are related.

S

scalability
The characteristic that allows a system to grow to accommodate increased usage. On Tandem systems, scalability is achieved largely through parallel processing.

security service
An application service that verifies user identity as a means of restricting certain operations to users with proper identification (authentication).

sequence
IDL sequences can be bounded or unbounded. They are mapped to a C++ class that has a current length and a maximum length and a _var type for the data.

servant
An entity residing in a server. NonStop servants are C++ object instances. A servant answers the client service request.

servant manager
A POA component that acts on demand from the ORB to activate or deactivate servants. The servant manager associates an ORB object with the appropriate servant. The two types of managers are ServantActivator and ServantLocater. POA policies determine which of the managers will be used.

server
In object technology, an application component that satisfies the requests of a client by providing an execution space ("hosting") one or more objects invoked by the client. More generally, an application component that services the requests of a client. A server program is the source code for a server.

server class
NonStop TS/MP term synonymous with a server pool.

server event handler
A NonStop DOM Event that supports asynchronous communication of a server and of a connection between a NonStop DOM server and a client using other technology by transferring data across the connection established by a listener event handler, for example, a NonStop DOM server or a client wrapper.

server pool
A set of processes that run the same program in parallel to increase the throughput and fault-tolerance of an application. A NonStop DOM application can use server pools managed by NonStop Transaction Services/MP (NonStop TS/MP).

service
A set of related functions available to applications on a system or network. See also Common Object Services.

setting
In general, the value of a parameter or variable. In NonStop DOM, a value specified in a configuration file.

Shared Runtime Library (SRL)
An object file that the operating system links to a program at runtime.

skeleton
Entity residing on the server. A NonStop DOM skeleton is a C++ base class containing pointers to servant methods. The base class is generated by the IDL compiler. The skeleton connects the servant to an object adapter.

skeleton script
The initial script used by the installation and configuration program that contains the information to install and configure a default NonStop DOM system. This script is used after the unpax, soliciting the ORB name and $volume.subvolume.

socket
A logical connection to the TCP/IP process.

stateful processing
Application logic in which all method invocations directed to the same object, for the duration of a link acquired by the client, must be handled by the same servant. Method invocations to other objects in the class can be handled by different servants in other processes. A stateful object allows the servant to retain its information and data values between method calls. Stateful objects are created by a POA whose IdAssignment policy is TRANSIENT, such as the root POA. This is the default behavior for objects as specified by the root POA.

Static Invocation Interface (SII)
A request style in which the client must know the object interface (the calling sequence for requesting specific operations) at compile time. Contrast Dynamic Invocation Interface.

stateless processing
A style of application logic in which method invocations directed to the same object can result in requests to different servants residing in different processes in a server pool. This style is selected by using an IdAssignment policy of PERSISTENT for the POA which creates the object reference, and by enabling the NonStop TS/MP protocol in the server. This is called stateless because, typically, the object state resides on disc (hence persistent) and not within the servant or process memory (hence the servant is stateless).

Structured Query Language (SQL)
A standard technology for defining and using relational databases. NonStop SQL/MP is the Tandem implementation of this standard.

subclass
An object class that inherits characteristics from another object class.

subnet
An abstraction meaningful to NonStop TCP/IP, which defines the relationship between a TCP/IP process, one or more TLAM processes, and one or more Internet (IP) addresses.

Subsystem Control Facility (SCF)
The interactive utility for configuration, monitoring, and control of networking resources on a Tandem NonStop System.

Subsystem Programmatic Interface (SPI)
A set of conventions that provide a uniform way to automate the management of many Tandem products. In general, a management programming interface based on SPI makes available the same set of services available to an operator through the corresponding interactive utility. For example, NonStop TS/MP offers a management programming interface that gives applications access to the same set of functions available through PATHCOM.

T

Tandem Information Manager (TIM)
A program that permits users to search electronically for information about Tandem products. The sources of information can be Tandem manuals, softdocs, or other literature stored on CD-ROMs or on the World Wide Web.

Tandem LAN Access Method
A software product that supports connections between Tandem NonStop Systems and other computers and devices across a local area network. TLAM supports the following communications protocols: IEEE 802.2 logical link control 1, Ethernet, IEEE 802.3, and IEEE 802.5.

Tandem X.25 Access Method
See X25AM.

Tcl
See Tool Command Language.

TCP/IP (Transmission Control Protocol/Internet Protocol)
One of the most widespread networking protocols, the basis for communications on the Internet. The CORBA IIOP protocol uses TCP/IP as its transport service. The Tandem product that implements TCP/IP is NonStop TCP/IP.

threads
A means of allowing a process to work on multiple tasks at once by creating a separate logical flow (thread) for each task and providing a mechanism for the process to switch among tasks in progress. NonStop DOM and its applications use a threads package equivalent to the DCE threads package. Threads differ from server pools in that threads require the same process to handle multiple requests, whereas server pools allow requests to be handled by different processes running in parallel. Server tool processes may be threaded.

three-tiered architecture
See tiered application architecture.

tiered application architecture
An application model in which function is divided into a few major categories of objects, such as interface, control, and entity objects.

TIM
See Tandem Information Manager (TIM).

TLAM
See Tandem LAN Access Method.

Tool Command Language (TCL)
The Command Line Interface used in NonStop DOM. TCL provides a wide variety of services and is a powerful aid for development, testing, and deployment.

trace
A sequential record of data or program flow, useful for troubleshooting. NonStop DOM includes facilities to trace the flow of control within an application.

transaction
A series of logically related operations. A transaction is complete only when all operations in the series have been performed. This manual makes a distinction between "user" or "application transactions," which are defined and controlled by application components, and "services transactions," which are defined and controlled by objects services such as the Naming Service.

transaction management
A set of tasks required to ensure satisfactory transaction processing. Transaction management includes transaction control (the application logic that determines when a transaction starts and stops, and when and how to abort a transaction), transaction protection, and auditing (logging the progress of transactions, to support request tracking and recovery). A NonStop DOM application controls transactions by using the Object Transaction Service (OTS).

transaction protection
A feature that ensures consistency of databases and other stored data.

transaction service
A standard application service (one of the OMG Common Object Services) for ensuring the consistency of a database or other stored information when a request involves multiple updates to databases or state repositories.

Tuxedo enterprise transaction processing system
The Novell, Inc. transaction processing system. The NonStop Tuxedo system is the Tandem implementation of this technology.

U

usage binding
See binding.

W

wrapping
A technique in which a component is given an interface that permits interoperation with components based on a different technology. For example, a set of interacting C++ object classes can be wrapped in a single NonStop DOM class, or the code of a legacy server can be used as the implementation of an object supporting methods that correspond to functions of the server.

A recommended approach to wrapping is to develop a wrapper component that translates method invocations to some other message format, or vice versa, to allow communication between object-oriented and legacy clients and servers.

widening
A term used in CORBA when moving from a derived interface to a base interface. C++ refers to this as up-cast.

X

X25AM
A Tandem product that supports connections between Tandem systems and other computers and devices across wide area networks, using X.25 protocol.

X.25
A CCITT recommendation for wide area, packet-switched networking. The Tandem product that implements X.25 is called X25AM.


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