access control

A feature of Oracle Connection Manager that sets rules for denying or allowing certain clients to access designated servers.

access control list (ACL)

The group of access directives that you define. The directives grant levels of access to specific data for specific clients or groups of clients.


See protocol address.


An alternative name for a network object in an Oracle Names server. An alias stores the name of the object is referencing. When a client requests a lookup of an alias, Oracle completes the lookup as if it is the referenced object.

application gateway

A host computer that runs the Oracle Net Firewall Proxy. An application gateway looks and acts like a real server from the client's point of view, and a real client from the server's point of view. An application gateway sits between the Internet and company's internal network and provides middleman services (or proxy services) to users on either side.

ASCII character set

American Standard Code for Information Interchange character set, a convention for representing alphanumeric information using digital data. The collation sequence used by most computers with the exception of IBM and IBM-compatible computers.


A piece of information that describes some aspect of a directory entry. An entry comprises a set of attributes, each of which belongs to an object class. Moreover, each attribute has both a type, which describes the kind of information in the attribute, and a value which contains the actual data.

authentication method

A security method that enables you to have confidence in the identity of users, clients, and servers in distributed environments. Network authentication methods can also provide the benefit of single sign-on for users. The following authentication methods are supported in Oracle Database, depending on whether Oracle Advanced Security is installed:

Automatic Diagnostic Repository (ADR)

A systemwide tracing and logging central repository. The repository is a file-based hierarchical data store for depositing diagnostic information, including network tracing and logging information.


Memory that stores recently-accessed data to so that subsequent requests to access the same data can be processed quickly.

CIDR (Classless Inter-Domain Routing)


A user, software application, or computer that requests the services, data, or processing from another application or computer. The client is the user process.

client load balancing

Load balancing, whereby if more than one listener services a single database, a client can randomly choose between the listeners for its connect requests. This randomization enables all listeners to share the burden of servicing incoming connect requests.

client profile

The properties of a client, which may include the preferred order of naming methods, client and server logging and tracing, the domain from which to request names, and other client options for Oracle Advanced Security.

client/server architecture

Software architecture based on a separation of processing between two CPUs. One CPU acts as the client in the transaction, requesting and receiving services. The other acts as the server that provides service for the requests.

cman.ora file

A configuration file that specifies protocol addresses for incoming requests and administrative commands, as well as Oracle Connection Manager parameters and access control rules.

CMADMIN (Connection Manager Administration)

An Oracle Connection Manager process that monitors the health of the listener and Oracle Connection Manager gateway processes, shutting down and starting processes as needed. CMADMIN registers information about gateway processes with the listener and processes commands executed with the Oracle Connection Manager Control utility.

CMGW (Connection Manager gateway)

An Oracle Connection Manager process that receives client connections screened and forwarded by the listener located at the Oracle Connection Manager instance. The gateway process forwards the requests to the database server. In addition, it can multiplex or process multiple client connections through a single protocol connection.

connect data

A portion of the connect descriptor that defines the destination database service name or Oracle System Identifier (SID). In the following example, SERVICE_NAME defines a database service called


connect descriptor

A specially-formatted description of the destination for a network connection. A connect descriptor contains destination service and network route information.

The destination service is indicated by using its service name. The network route provides, at a minimum, the location of the listener through use of a network address.

connect identifier

A name, net service name, or service name that resolves to a connect descriptor. Users initiate a connect request by passing a user name and password along with a connect identifier in a connect string for the service to which they want to connect, for example:

CONNECT username@connect_identifier 

connect string

Information the user passes to a service to connect, such as user name, password, and connect identifier:

CONNECT username@net_service_name

connect-time failover

A connect-time failover occurs when a client connect request fails over to a different address if the first protocol address fails. A statically configured global database name disables connect-time failover.


An interaction between two processes on a network. Connections are originated by an initiator (client) that requests a connection with a destination (server).

connection load balancing

The method for balancing the number of active connections for the same service across the instances and dispatchers. Connection load balancing enables listeners to make routing decisions based on how many connections for each dispatcher and the load on the nodes.

connection pooling

A resource utilization and user scalability feature that enables you to maximize the number of sessions over a limited number of protocol connections to a shared server.

connection request

A notification sent by an initiator and received by a listener that indicates that the initiator wants to start a connection.

data packet

See packet.

database administrator (DBA)

A person responsible for operating and maintaining an Oracle Server or a database application.

An Oracle user name that has been given DBA privileges and can perform database administration functions. Usually the two meanings coincide. Many sites have multiple DBAs.

Database Configuration Assistant

A tool that enables you to create, delete, and modify a database.

database link

A pointer that defines a one-way communication path from an Oracle database server to another database server. The link is a defined entry in a data dictionary table. To access the link, the user must be connected to the local database that contains the data dictionary entry.

A client connected to local database A can use a link stored in database A to access information in remote database B. However, users connected to database B cannot use the same link to access data in database A. If local users on database B want to access data on database A, then a link must be defined and stored in the data dictionary of database B.

The following database links are supported:

dedicated server

A server process that is dedicated to one client connection. Compare to shared server.

default domain

The domain within which most client requests take place. It could be the domain where the client resides, or it could be a domain from which the client requests network services often. Default domain is also the client configuration parameter that determines what domain should be appended to unqualified network name requests. A name request is unqualified if it does not have a period (.) character within it.

directory information tree (DIT)

A hierarchical tree-like structure in a directory server of the distinguished names (DNs) of the entries.

directory naming

A naming method that resolves a database service, net service name, or net service alias to a connect descriptor stored in a central directory server. A directory server provides central administration of directory naming objects, reducing the work effort associated with adding or relocating services.

directory server

A directory server that is accessed with the Lightweight Directory Access Protocol (LDAP). Support of LDAP-compliant directory servers provides a centralized vehicle for managing and configuring a distributed Oracle network. The directory server can replace client-side and server-side localized tnsnames.ora files.


A process that enables many clients to connect to the same server without the need for a dedicated server process for each client. A dispatcher handles and directs multiple incoming network session requests to shared server processes. See also shared server.

distinguished name (DN)

Name of entry in a directory server. The DN specifies where the entry resides in the LDAP directory hierarchy, much the way a directory path specifies the exact location of a file.

distributed processing

Division of front-end and back-end processing to different computers. Oracle Net Services support distributed processing by transparently connecting applications to remote databases.


Any tree or subtree within the Domain Name System (DNS) namespace. Domain most commonly refers to a group of computers whose host names share a common suffix, the domain name.

Domain Name System (DNS)

A system for naming computers and network services that is organized into a hierarchy of domains. DNS is used in TCP/IP networks to locate computers through user-friendly names. DNS resolves a friendly name into an IP address, which is understood by computers.

For Oracle Net Services, DNS translates the host name in a TCP/IP address into an IP address.

enterprise role

An enterprise role is analogous to a regular database role, except that it spans authorization on multiple databases. An enterprise role is a category of roles that define privileges on a particular database. An enterprise role is created by the database administrator of a particular database. An enterprise role can be granted to or revoked to one or more enterprise users. The information for granting and revoking these roles is stored in the directory server.

enterprise user

A user that has a unique identity across an enterprise. Enterprise users connect to individual databases through a schema. Enterprise users are assigned enterprise roles that determine their access privileges on databases.


The building block of a directory server, it contains information about an object of interest to directory users.

external naming

A naming method that uses a third-party naming service, such as NIS.

external procedure

Function or procedure written in a third-generation language (3GL) that can be called from PL/SQL code. Only C is supported for external procedures.


See connect-time failover.

firewall support

See access control.

foreign domains

The set of domains not managed within a given administrative region. Domains are foreign only in relation to a region; they are not foreign in any absolute sense. A network administrator typically defines foreign domains relative to a particular region to optimize caching performance.


File Transfer Protocol. A client/server protocol which allows a user on one computer to transfer files to and from another computer over a TCP/IP network.

global database name

The full name of the database which uniquely identifies it from any other database. The global database name is of the form "database_name.database_domain," for example,

The database name portion, sales, is a simple name to call a database. The database domain portion,, specifies the database domain in which the database is located, making the global database name unique. When possible, Oracle recommends that your database domain mirror the network domain.

The global database name is the default service name of the database, as specified by the SERVICE_NAMES parameter in the initialization parameter file.

Heterogeneous Services

An integrated component that provides the generic technology for accessing non-Oracle systems from the Oracle database server. Heterogeneous Services enables you to:

  • Use Oracle SQL to transparently access data stored in non-Oracle systems as if the data resides within an Oracle server.

  • Use Oracle procedure calls to transparently access non-Oracle systems, services, or application programming interfaces (APIs), from your Oracle distributed environment.

hierarchical naming model

An infrastructure in which names are divided into multiple hierarchically-related domains. For Oracle Names, hierarchical naming model can be used with either central or delegated administration.

host naming

A naming method resolution that enables users in a TCP/IP environment to resolve names through their existing name resolution service. This name resolution service might be Domain Name System (DNS), Network Information Service (NIS), or simply a centrally-maintained set of /etc/hosts files. Host naming enables users to connect to an Oracle database server by simply providing the server computer's host name or host name alias. No client configuration is required to take advantage of this feature. This method is recommended for simple TCP/IP environments.


Hypertext Transfer Protocol. A protocol that provides the language that enables Web browsers and application Web servers to communicate.

identity management realm

A collection of identities, all of which are governed by the same administrative policies. In an enterprise, all employees having access to the intranet may belong to one realm, while all external users who access the public applications of the enterprise may belong to another realm. An identity management realm is represented in the directory by a specific entry with a special object class associated with it.


The combination of the System Global Area (SGA) and the Oracle background processes. When a database is started on a database server (regardless of the type of computer), Oracle allocates a memory area called the SGA, and starts one or more Oracle processes. The memory and processes of an instance efficiently manage the associated database data and serve the database users. You can connect to any instance to access information within a cluster database.

instance name

A name of an Oracle database instance. The instance name is identified by the INSTANCE_NAME parameter in the database initialization parameter file. INSTANCE_NAME corresponds to the Oracle System Identifier (SID) of the instance. Clients can connect to a specific instance by specifying the INSTANCE_NAME parameter in the connect descriptor.

The instance name is included in the connect data part of the connect descriptor.

Interprocess Communication (IPC)

A protocol used by client applications that resides on the same node as the listener to communicate with the database. IPC can provide a faster local connection than TCP/IP.

IP address

Used to identify a node on a network. Each computer on the network is assigned a unique IP address, which is made up of the network ID, and a unique host ID. This address is typically represented in dotted-decimal notation, with the decimal value of each octet separated by a period, for example

Java Database Connectivity (JDBC) Driver

A driver that provides Java applications and applets access to an Oracle database.


A Type II driver for use with client/server Java applications. This driver requires an Oracle client installation.

JDBC Thin Driver

A Type IV driver for Oracle JDBC applets and applications. Because it is written entirely in Java, this driver is platform-independent. It does not require any additional Oracle software on the client side. The Thin driver communicates with the server using Two-Task Common (TTC), a protocol developed by Oracle to access the database server.

keyword-value pair

The combination of a keyword and a value, used as the standard unit of information in connect descriptors and many configuration files. Keyword-value pairs may be nested; that is, a keyword may have another keyword-value pair as its value.


The amount of time it takes for to send a request and receive an answer.

LDAP Data Interchange Format (LDIF)

The set of standards for formatting an input file for any of the LDAP command line utilities.

ldap.ora file

A file created by Oracle Internet Directory Configuration Assistant or Oracle Net Configuration Assistant that contains the following directory server access information:

  • Type of directory server

  • Location of the directory server

  • Default Oracle Context that the client or server use to look up or configure connect identifiers for connections to database services

When created with Oracle Internet Directory Configuration Assistant, ldap.ora is located in the ORACLE_HOME/ldap/admin directory. When created with Oracle Net Configuration Assistant, ldap.ora is located in the ORACLE_HOME/network/admin directory.

Lightweight Directory Access Protocol (LDAP)

A standard, extensible directory access protocol. It is a industry-standard programmatic interface and a wire protocol which enables clients to access directory systems.

link qualifier

An extension to the database link name which specifies the connect name used to connect to the database. It provides alternate settings for the database user name and password credentials. For example, a link qualifier of fieldrep can be appended to a global database link of



A process that resides on the server whose responsibility is to listen for incoming client connection requests and manage the traffic to the server.

When a client requests a network session with a database server, a listener receives the actual request. If the client information matches the listener information, then the listener grants a connection to the database server.

Listener Control utility

A utility included with Oracle Net Services to control listener functions, such as starting, stopping, and getting the status of the listener.

listener.ora file

A configuration file for the listener that identifies the following for a listener:

  • Unique name

  • Protocol addresses that it is accepting connection requests on

  • Services it is listening for

The listener.ora file typically resides in the ORACLE_HOME/network/admin directory.

Oracle does not require identification of the database service because of service registration. However, static service configuration is required if you plan to use Oracle Enterprise Manager.

load balancing

A feature by which client connections are distributed evenly among multiple listeners, dispatchers, instances, and nodes so that no single component is overloaded.

Oracle Net Services support client load balancing and connection load balancing.

local naming

A naming method that locates network addresses by using information configured and stored on each individual client's tnsnames.ora file. Local naming is most appropriate for simple distributed networks with a small number of services that change infrequently.

location transparency

A distributed database characteristic that enables applications to access data tables without knowing where they reside. All data tables appear to be in a single database, and the system determines the actual data location based on the table name. The user can reference data on multiple nodes in a single statement, and the system automatically and transparently routes (parts of) SQL statements to remote nodes for execution if needed. The data can move among nodes with no impact on the user or application.


A feature in which errors, service activity, and statistics are written to a log file. The log file provides additional information for an administrator when the error message on the screen is inadequate to understand the failure. The log file, by way of the error stack, shows the state of the software at various layers.

See also tracing.

loopback test

A connection from the server back to itself. Performing a successful loopback verifies that Oracle Net is functioning on the database server.


Files used by the Network Information Service (NIS) ypserv program to handle name requests.

Microsoft Active Directory

An LDAP-compliant directory server included with Microsoft Windows 2000 Server. It stores information about objects on the network, and makes this information available to users and network administrators. Active Directory also provides access to resources on the network using a single logon process.

Active Directory can be configured as a directory naming method to store service information that clients can access.

Microsoft Windows NT native authentication

An authentication method that enables a client single login access to a Microsoft Windows NT server and a database running on the server.

Named Pipes protocol

A high-level interface protocol providing interprocess communications between clients and servers using distributed applications. Named Pipes enables client/server conversation over a network using Named Pipes protocol.

naming context

A subtree that resides entirely on one directory server. It is a contiguous subtree, that is, it must begin at an entry that serves as the top of the subtree, and extend downward to either leaf entries or references to subordinate naming contexts. It can range in size from a single entry to the entire directory information tree (DIT).

An Oracle Context can be created under a naming context.

naming method

The resolution method used by a client application to resolve a connect identifier to a connect descriptor when attempting to connect to a database service. Oracle Net provides four naming methods:

net service alias

An alternative name for a directory naming object in a directory server. A directory server stores net service aliases for any defined net service name or database service. A net service alias entry does not have connect descriptor information. Instead, it only references the location of the object for which it is an alias. When a client requests a directory lookup of a net service alias, the directory determines that the entry is a net service alias and completes the lookup as if it was actually the entry it is referencing.

net service name

A simple name for a service that resolves to a connect descriptor. Users initiate a connect request by passing a user name and password along with a net service name in a connect string for the service to which they want to connect:

CONNECT username/password@net_service_name

Depending on your needs, net service names can be stored in a variety of places, including:

  • Local configuration file, tnsnames.ora, on each client

  • Directory server

  • External naming service, such as NIS


A group of two or more computers linked through hardware and software to allow the sharing of data and peripherals.

network administrator

The person who performs network management tasks such as installing, configuring, and testing network components. The administrator typically maintains the configuration files, connect descriptors and service names, aliases, and public and global database links.

network character set

As defined by Oracle, the set of characters acceptable for use as values in keyword-value pairs (that is, in connect descriptors and configuration files). The set includes alphanumeric uppercase, and lowercase, and some special characters.

Network Information Service (NIS)

Sun Microsystems' Yellow Pages (yp) client/server protocol for distributing system configuration data such as user and host names between computers on a network.

Network Interface (NI)

A network layer that provides a generic interface for Oracle clients, servers, or external processes to access Oracle Net functions. The NI layer handles the break and reset requests for a connection.

network listener

See listener.

network object

Any service that can be directly addressed on a network; for example, a listener.

Network Program Interface (NPI)

An interface for server-to-server interactions that performs all of the functions that the OCI does for clients, allowing a coordinating server to construct SQL requests for additional servers.

network protocol

See Oracle protocol support.

Network Session (NS)

A session layer that is used in typical Oracle Net connections to establish and maintain the connection between a client application and a database server.


A computer or terminal that is part of a network


Network Transport. See transport.

object class

In a directory server, a named group of attributes. When you want to assign attributes to an entry, you do so by assigning the object classes that hold those attributes to that entry.

All objects associated with the same object class share the attributes of that object class.

Open Systems Interconnection (OSI)

A network architecture model developed by ISO as a framework for international standards in heterogeneous computer network architecture.

The OSI architecture has seven layers, from lowest to highest:

1. Physical layer

2. Data link layer

3. Network layer

4. Transport layer

5. Session layer

6. Presentation layer

7. Application layer

Oracle Advanced Security

A comprehensive suite of security features to protect enterprise networks and securely extends corporate networks to the Internet. Oracle Advanced Security provides a single source of integration with network encryption and authentication solutions, single sign-on services, and security protocols. By integrating industry standards, it delivers unparalleled security to the network.

Oracle Call Interface (OCI)

An application programming interface (API) that enables you to create applications that use the native procedures or function calls of a third-generation language to access an Oracle database server and control all phases of SQL statement execution. OCI supports the data types, calling conventions, syntax, and semantics of a number of third-generation languages including C, C++, COBOL and FORTRAN.

Oracle Connection Manager

A router through which a client connection request may be sent either to its next hop or directly to the database server. Clients who route their connection requests through an Oracle Connection Manager can take advantage of the session multiplexing, access control, or protocol conversion features configured for that Oracle Connection Manager.

Oracle Connection Manager Control utility

A utility included with Oracle Net Services to control various functions, such as starting, stopping, and getting the status of the Oracle Connection Manager.

Oracle Context

A relative distinguished name (RDN) of cn=OracleContext in a directory information tree (DIT) that is located under a naming context or an unpublished directory entry. Oracle Context contains entries for use with Oracle features, such as Oracle Net directory naming and Oracle Advanced Security enterprise user security. There can be one or more Oracle Contexts in a directory server. Oracle Internet Directory automatically creates an Oracle Context at the root of the DIT structure. This root Oracle Context has a DN of dn:cn=OracleContext.

Oracle Enterprise Manager

A separate Oracle product that combines a graphical console, agents, common services, and tools to provide an integrated and comprehensive systems management platform for managing Oracle products.

Oracle Identity Management

An infrastructure enabling deployments to manage centrally and securely all enterprise identities and their access to various applications in the enterprise.

Oracle Internet Directory

A directory server implemented as an application on the Oracle database. It enables retrieval of information about dispersed users and network resources. It combines Lightweight Directory Access Protocol (LDAP) Version 3, the open Internet standard directory server access protocol, with the high performance, scalability, robustness, and availability of the Oracle database.

Oracle Net

Communication software that enables a network session from a client application to an Oracle database server. After a network session is established, Oracle Net acts as a data courier for the client application and the database server. It is responsible for establishing and maintaining the connection between the client application and database server, as well as exchanging messages between them. Oracle Net can perform these jobs because it is located on each computer in the network.

Oracle Net Configuration Assistant

A postinstallation tool that configures basic network components after installation, including:

  • Listener names and protocol addresses

  • Naming methods the client uses to resolve connect identifiers

  • Net service names in a tnsnames.ora file

  • Directory server usage

Oracle Net Firewall Proxy

Product offered by some firewall vendors that supplies Oracle Connection Manager functionality.

Oracle Net foundation layer

A networking communication layer that is responsible for establishing and maintaining the connection between the client application and server, as well as exchanging messages between them.

Oracle Net listener

See listener.

Oracle Net Manager

A tool that combines configuration abilities with component control to provide an integrated environment for configuring and managing Oracle Net Services.

You can use Oracle Net Manager to configure the following network components:

  • Naming

    Define connect identifiers and map them to connect descriptors to identify the network location and identification of a service. Oracle Net Manager supports configuration of connect descriptors in a local tnsnames.ora file or directory server.

  • Naming Methods

    Configure the ways in which connect identifiers are resolved into connect descriptors.

  • Listeners

    Create and configure listeners to receive client connections.

Oracle Net Services

A suite of networking components that provide enterprise-wide connectivity solutions in distributed, heterogeneous computing environments. Oracle Net Services is comprised of Oracle Net, listener, Oracle Connection Manager, Oracle Net Configuration Assistant, and Oracle Net Manager.

Oracle Program Interface (OPI)

A networking layer responsible for responding to each of the possible messages sent by OCI. For example, an OCI request to fetch 25 rows would have an OPI response to return the 25 rows after they have been fetched.

Oracle protocol support

A software layer responsible for mapping Transparent Network Substrate (TNS) functionality to industry-standard protocols used in the client/server connection.

Oracle Rdb

A database for Digital's 64-bit platforms. Because Oracle Rdb has its own listener, the client interacts with Rdb in the same manner as it does with an Oracle database.

Oracle schema

A set of rules that determine what can be stored in a directory server. Oracle has its own schema that is applied to many types of Oracle entries, including Oracle Net Services entries. The Oracle schema for Oracle Net Services entries includes the attributes the entries may contain.

Oracle System Identifier (SID)

A name that identifies a specific instance of a running an Oracle database earlier than release 8.1. For any database, there is at least one instance referencing the database.

For Oracle databases earlier than release 8.1, a SID is used to identify the database. The SID is included in the connect descriptor of a tnsnames.ora file and in the definition of the listener in the listener.ora file.

Oracle XML DB

A high-performance XML storage and retrieval technology provided with Oracle database server. It is based on the W3C XML data model.

Oracle Real Application Clusters

An architecture that allows multiple instances to access a shared database of data files. Oracle Real Application Clusters is also a software component that provides the necessary cluster database scripts, initialization files, and data files needed for the Oracle Enterprise Edition and Oracle Real Application Clusters.


An alternate name for the top directory in the Oracle directory hierarchy on some directory-based operating systems.


A block of information sent over the network each time a connection or data transfer is requested. The information contained in packets depends on the type of packet, such as connect, accept, redirect, data, and so on. Packet information can be useful in troubleshooting.

PMON process

A process monitor (PMON) database process that performs process recovery when a user process fails. PMON is responsible for cleaning the cache and freeing resources that the process was using. PMON also checks on dispatcher and server processes and restarts them if they have failed. As a part of service registration, PMON registers instance information with the listener.

presentation layer

A networking communication layer that manages the representation of information that application layer entities either communicate or reference in their communication. Two-Task Common (TTC) is an example of presentation layer.

private database link

A database link created by one user for exclusive use.

See also database link and public database link.


A collection of parameters that specifies preferences for enabling and configuring Oracle Net Services features on the client or server. A profile is stored and implemented through the sqlnet.ora file.


A set of rules that defines how data is transported across the network.

protocol address

An address that identifies the network address of a network object.

When a connection is made, the client and the receiver of the request, such as the listener or Oracle Connection Manager, are configured with identical protocol addresses. The client uses this address to send the connection request to a particular network object location, and the recipient listens for requests on this address. It is important to install the same protocols for the client and the connection recipient, as well as configure the same addresses.

protocol conversion

A feature of Oracle Connection Manager that enables a client and server with different networking protocols to communicate with each other. This feature replaces functionality previously provided by the Oracle Multi-Protocol Interchange with SQL*Net version 2.

protocol stack

Designates a particular presentation layer and session layer combination.

proxy server

A server that substitutes for a real server, forwarding client connection requests to the real server or to other proxy servers. Proxy servers provide access control, data and system security, monitoring, and caching.

public database link

A database link created by a DBA on a local database that is accessible to all users on that database.

See also database link and private database link.

realm Oracle Context

An Oracle Context contained in each identity management realm. It stores the following information:

  • User naming policy of the identity management realm, that is, how users are named and located

  • Mandatory authentication attributes

  • Location of groups in the identity management realm

  • Privilege assignments for the identity management realm, for example, who has privileges to add more users to the realm.

  • Application specific data for that realm including authorizations


Relational Database Management System.

relative distinguished name (RDN)

A fully-qualified X.500 name. It is the local, most granular level entry name. In the example, cn=sales,dc=us,dc=acme,dc=com, the RDN is cn=sales.

root Oracle Context

In the Oracle Identity Management infrastructure, the root Oracle Context is an entry in Oracle Database Net Services Reference containing a pointer to the default identity management realm in the infrastructure. It also contains information about how to locate an identity management realm given the simple name of the realm.


Remote procedure call.


Sockets Direct Protocol.

Secure Sockets Layer (SSL)

An industry-standard protocol designed by Netscape Communications Corporation for securing network connections. SSL provides authentication, encryption, and data integrity using public key infrastructure (PKI).

server process

Database processes that handle a client request on behalf of a database.


A program that responds to requests from various clients or performs some operation. For example, the database is a service that stores and retrieves data for clients.

service handler

A process that acts a connection point from the listener to the database server. A service handler can be a dispatcher or dedicated server.

service name

A logical representation of a database, which is the way a database is presented to clients. A database can be presented as multiple services and a service can be implemented as multiple database instances. The service name is a string that is the global database name, that is, a name comprising the database name and domain name, entered during installation or database creation. If you are not sure what the global database name is, then you can obtain it from the value of the SERVICE_NAMES parameter in the initialization parameter file.

The service name is included in the connect data part of the connect descriptor.

service registration

A feature by which the PMON process automatically registers information with a listener. Because this information is registered with the listener, the listener.ora file does not need to be configured with this static information.

Service registration provides the listener with information about:

  • Service names for each running instance of the database

  • Instance names of the database

  • Service handlers (dispatcher or dedicated server) available for each instance

    These enable the listener to direct a client request appropriately.

  • Dispatcher, instance, and node load information

    This load information enables the listener to determine which dispatcher can best handle a client connection request. If all dispatchers are blocked, then the listener can spawn a dedicated server for the connection.

session data unit (SDU)

A buffer that Oracle Net uses to place data before transmitting it across the network. Oracle Net sends the data in the buffer either when requested or when it is full.

session layer

A network layer that provides the services needed by the protocol address entities that enable them to organize and synchronize their dialog and manage their data exchange. This layer establishes, manages, and terminates network sessions between the client and server. An example of a session layer is Network Session (NS).

session multiplexing

Combining multiple sessions for transmission over a single network connection to conserve the operating system's resources.

shared server

A database server that is configured to allow many user processes to share very few server processes, so the number of users that can be supported is increased. With shared server configuration, many user processes connect to a dispatcher. The dispatcher directs multiple incoming network session requests to a common queue. An idle shared server process from a shared pool of server processes picks up a request from the queue. This means that a small pool of server processes can serve a large number of clients. Contrast with dedicated server.

shared server process

A process type used with shared server configuration.


A section of the listener.ora file that defines the Oracle System Identifier (SID) of the database served by the listener. This section is valid only for Oracle databases release 8.0, as information for Oracle8i or later instances is automatically registered with the listener. Static configuration is also required for other services, such as external procedure calls and Heterogeneous Services.

single sign-on

The ability for a user to log in to different servers using a single password. This permits the user to authenticate to all servers the user is authorized to access.

sqlnet.ora file

A configuration file for the client or server that specifies:

  • Client domain to append to unqualified service names or net service names

  • Order of naming methods the client should use when resolving a name

  • Logging and tracing features to use

  • Route of connections

  • External naming parameters

  • Oracle Advanced Security parameters

The sqlnet.ora file typically resides in the ORACLE_HOME/network/admin directory.

System Global Area (SGA)

A group of shared memory structures that contain data and control information for an Oracle instance.


Transmission Control Protocol/Internet Protocol. The standard communication protocol used for client/server conversation over a network.

TCP/IP with SSL protocol

A protocol that enables an Oracle application on a client to communicate with remote Oracle databases through the TCP/IP and Secure Sockets Layer (SSL).


The amount of time it takes for a message to be sent and processed from the client to the server or from the server to the client

tnsnames.ora file

A configuration file that maps net service names to connect descriptors. This file is used for the local naming method. The tnsnames.ora file typically resides in the ORACLE_HOME/network/admin directory.


A facility that writes detailed information about an operation to an output file. The trace facility produces a detailed sequence of statements that describe the events of an operation as they are run. Administrators use the trace facility for diagnosing an abnormal condition. It is not normally turned on.

See also logging.

Transparent Application Failover (TAF)

A run-time failover for high-availability environments, such as Oracle Real Application Clusters and Oracle Fail Safe, that refers to the failover and re-establishment of application-to-service connections. It enables client applications to automatically reconnect to the database if the connection fails, and, optionally, resume a SELECT statement that was in progress. This reconnect happens automatically from within the Oracle Call Interface (OCI) library.

Transparent Network Substrate (TNS)

A foundation technology, built into the Oracle Net foundation layer that works with any standard network transport protocol.


A networking layer that maintains end-to-end reliability through data flow control and error recovery methods. The Oracle Net foundation layer uses Oracle protocol support for the transport layer.

Two-Task Common (TTC)

A presentation layer type that is used in a typical Oracle Net connection to provide character set and data type conversion between different character sets or formats on the client and server.


User Program Interface

virtual circuit

A piece of shared memory used by the dispatcher for client database connection requests and replies. The dispatcher places a virtual circuit on a common queue when a request arrives. An idle shared server picks up the virtual circuit from the common queue, services the request, and relinquishes the virtual circuit before attempting to retrieve another virtual circuit from the common queue.

WebDAV protocol

World Wide Web Distributed Authoring and Versioning. A protocol with a set of extensions to HTTP which allows users to manage files on remote Web servers.