This chapter describes the basic elements of Oracle Net Services architecture and the Oracle Net foundation layer.
This chapter contains the following topics:
Oracle Net Services provides enterprise wide connectivity solutions in distributed, heterogeneous computing environments. Oracle Net Services ease the complexities of network configuration and management, maximize performance, and improve network diagnostic capabilities.
This section introduces the basic networking concepts involved in a typical network configuration. The topics include:
Oracle Net, a component of Oracle Net Services, enables a network session from a client application to an Oracle Database server. Once a network session is established, Oracle Net acts as the data courier for both 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 is able to perform these jobs because it is located on each computer in the network.
This section discusses the following connectivity topics:
Oracle Net enables connections from traditional client/server applications to Oracle Database servers. Figure 1-1 shows how Oracle Net enables a network connection between a client and a database server. Oracle Net is a software component that resides on both the client and the database server. Oracle Net is layered on top of a network Oracle protocol support—rules that determine how applications access the network and how data is subdivided into packets for transmission across the network. In this illustration, Oracle Net communicates with the TCP/IP protocol to enable computer-level connectivity and data transfer between the client and the database server.
Specifically, Oracle Net is comprised of the Oracle Net foundation layer, which establishes and maintains connections, and Oracle protocol support, which maps the foundation layer's technology to industry-standard protocols.
Java client applications access an Oracle Database through a Java Database Connectivity (JDBC) Driver, a standard Java interface for connecting from Java to a relational database. Oracle offers the following drivers:
JDBC OCI Driver for client side use with an Oracle client installation
JDBC Thin Driver, a pure Java driver for client side use without an Oracle installation, particularly with applets
These drivers use Oracle Net to enable connectivity between a client application and an Oracle Database.
Figure 1-2 shows a Java client application using a JDBC OCI driver and an Oracle Database server. The Java client application makes calls to the JDBC OCI driver, which in turn translates the JDBC calls directly into the Oracle Net layer. The client then uses Oracle Net to communicate with an Oracle Database that is also configured with Oracle Net.
Internet connections from client Web browsers to an Oracle Database server are similar to client/server applications, except that the connection request goes over an application Web server.
Figure 1-3 shows the basic architecture for Web client connections, including a client Web browser, an application Web server, and an Oracle Database server. The browser on the client communicates with the HTTP protocol to a Web server to make a connection request. The Web server sends the request to an application where it is processed. The application then uses Oracle Net to communicate with an Oracle Database server that also is configured with Oracle Net.
The basic components have the following characteristics:
Hypertext Transport Protocol (HTTP)
HTTP provides the language that enables Web browsers and application Web servers to communicate.
An application Web server manages data for a Web site, controls access to that data, and responds to requests from Web browsers. The application on the Web server communicates with the database and performs the job requested by the Web server.
An application Web server can host Java applications and servlets, as shown in Figure 1-4. Web browsers make a connection request by communicating through HTTP to an application Web server. The application Web server sends the request to an application or a servlet, which in turn uses a JDBC OCI or a JDBC Thin driver to process the request. The driver then uses Oracle Net to communicate with an Oracle Database server that also is configured with Oracle Net.
Web clients that do not require an application Web server to access applications can access the Oracle Database directly, for example, by using a Java applet. In addition to regular connections, the database can be configured to accept HTTP protocol, FTP protocol, or WebDAV protocol connections. These protocols are used for connections to Oracle XML DB in the Oracle Database instance.
Figure 1-5 shows two different Web clients. The first Web client makes an HTTP connection to the database. The second Web client uses a Web browser with a JDBC Thin driver, which in turn uses a Java version of Oracle Net called JavaNet to communicate with the Oracle Database server that is configured with Oracle Net.
See Also:Oracle XML DB Developer's Guide
Oracle Net Services offer a number of manageability features that enable you to easily configure and manage networking components. These features are described in the following topics:
A company can have several databases, each representing a specific type of service for various client applications. For example, a company may have three databases, which it uses for sales, human resources, and marketing applications. Each database is represented by one or more services. A service is identified by a service name, for example,
sales.us.example.com. A client uses this service name to identify the database it must access. The information about the database service and its location in the network is transparent to the client because the information needed for a connection is stored in a repository.
For example, in Figure 1-6, a company has three databases that clients can access. Each database has a distinct service name:
The client uses the repository to find the information it needs for
Once the client has the information it needs, it connects to the database.
The repository is represented by one or more naming methods. Oracle Net Services offer several types of naming methods that support localized configuration on each client, or centralized configuration that can be accessed by all clients in the network. Easy-to-use graphical user interfaces enable you to manage data stored in the naming methods.
To manage large networking environments, administrators have to be able to easily access a centralized repository to specify and modify the network configuration. For this reason, the Oracle Net Services configuration can be stored in a LDAP-compliant directory server.
Support of LDAP-compliant directory servers provides a centralized vehicle for managing and configuring a distributed Oracle network. The directory can act as a central repository for all information on database network components, user and corporate policies, and user authentication and security, thus replacing client-side and server-side localized configuration files.
All computers on the heterogeneous network can refer to the directory for information. Figure 1-7 shows clients, other servers (such as application Web servers) and Oracle Database servers connecting to a centralized directory server.
See Also:"Directory ServerSupport" for an in-depth overview of directory server concepts
Oracle Net Services install quickly and easily. Networking elements for the Oracle Database server and clients are preconfigured for most environments. Information about an Oracle Database service is populated in one or more naming methods. As a result, clients and servers are ready to immediately connect when installed, giving users the benefits of distributed computing.
Oracle Net provides scalability features that enable you to maximize system resources and improve performance.
The Oracle Database shared server architecture increases the scalability of applications and the number of clients that can be simultaneously connected to the database. The shared server architecture also enables existing applications to scale up without making any changes to the application itself.
When using shared server, clients do not communicate directly with a database's server process—a database process that handles a client's requests on behalf of a database. Instead, client requests are routed to one or more dispatchers. The dispatchers place the client requests on a common queue. An idle shared server from the shared pool of server processes picks up and processes a request from the queue. This means a small pool of server processes can serve a large number of clients.
Figure 1-8 and Figure 1-9 show the basic difference between the shared server connection model and the traditional dedicated server connection model. In the shared server model, a dispatcher can support multiple client connections concurrently. In the dedicated server model, there is one server process for each client. Each time a connection request is received, a server process is started and dedicated to that connection until completed. This introduces a processing delay.
Shared server is ideal in configurations with a large number of connections because it reduces the server memory requirements. Shared server is well suited for both Internet and intranet environments.
Utilization of server resources can be further enhanced with Oracle Net Services features that are configurable through shared server. These features are discussed in the following sections:
When thousands of clients are running interactive Web applications, many of these sessions may be idle at a given time. The connection pooling feature enables the database server to timeout an idle session and use the connection to service an active session. The idle logical session remains open, and the physical connection is automatically reestablished when the next request comes from that session. Therefore, Web applications can allow larger numbers of concurrent users to be accommodated with existing hardware.
Figure 1-10 shows how connection pooling works. In this example, the Oracle Database server has been configured with 255 connections. One of the clients has been idle past a specified amount of time. Connection pooling makes this connection available to an incoming client connection, which is the 256th connection. When the idle client has more work to do, the connection is reestablished for that client with another client's idle connection.
Oracle Connection Manager, an Oracle Net Services component, enables multiple client network sessions to be multiplexed, or funneled, through a single network connection to a database.
The session multiplexing feature reduces the demand on resources needed to maintain multiple network sessions between two processes by enabling the server to use fewer network connection endpoints for incoming requests. In this way the total number of network sessions that a server can handle is increased. One Oracle Connection Manager with multiple gateways enables thousands of concurrent users to connect to a server.
Figure 1-11 shows how session multiplexing can be used in a Web architecture. When Oracle Connection Manager is run on the same computer as an application Web server, the application Web server can route multiple client sessions through Oracle Connection Manager to ensure that those sessions have continuous access to an Oracle Database server. This functionality is especially useful for Web applications where session availability and response time are major concerns.
Oracle Net Services provides support for Infiniband high-speed networks. InfiniBand is a high-bandwidth I/O architecture designed to increase communication speed between CPUs, server-side devices, and network subsystems. Specifically, Oracle Net Services provides support for the SDP protocol. SDP is an industry-standard wire protocol intended for use between Infiniband network peers.
SDP reduces the overhead of TCP/IP by eliminating intermediate replication of data and transferring most of the messaging burden away from the CPU and onto the network hardware. The result is a low-latency, increased bandwidth, high-throughput connection that reduces the amount of CPU cycles dedicated to network processing.
The communication between clients, including Oracle Application Server (OracleAS) or any other third-party middle-tier client, and an Oracle Database 11g database can take advantage of high-speed interconnect benefits. OracleAS installs with Oracle TCP/IP support.
A driver installed on the OracleAS servers transparently converts TCP/IP support to SDP support. The SDP requests are then sent to an Infiniband switch that processes and forwards the requests from the OracleAS servers to the database server. The SDP requests are then sent to an Infiniband switch that processes and forwards the requests from the OracleAS servers to the database server.
Data access and secure transfer of data are important considerations when deploying Oracle. Granting and denying access to a database is crucial for a secure network environment. Oracle Net Services enable database access control using features described in the following topics:
Oracle Connection Manager can be configured to grant or deny client access to a particular database service or a computer. By specifying filtering rules, you can allow or restrict specific client access to a server, based on the following criteria:
Source host names or IP addresses for clients
Destination host names or IP addresses for servers
Destination database service names
Client use of Oracle Advanced Security
Figure 1-12 shows an Oracle Connection Manager positioned between three Web clients and an Oracle Database server. Oracle Connection Manager is configured to allow access to the first two Web clients and to deny access to the third. In order for this configuration to work, clients require the JDBC Thin driver.
Although Oracle Connection Manager cannot currently be integrated with third-party firewall products, vendors can package it with their own products in a way that enables this product mix to serve as an application gateway.
Figure 1-13 shows an application gateway controlling traffic between internal and external networks and providing a single checkpoint for access control and auditing. As a result, unauthorized Internet hosts cannot directly access the database inside a corporation, but authorized users can still use Internet services outside the corporate network. This capability is critical in Internet environments to restrict remote access to sensitive data.
The connectivity, manageability, scalability, and security features described in this chapter are provided by the following components:
Oracle Net is a software layer that resides on the client and the Oracle Database server. It is responsible for establishing and maintaining the connection between the client application and server, as well as exchanging messages between them, using industry-standard protocols. Oracle Net is comprised of two software components:
On the client side, applications communicate with Oracle Net foundation layer to establish and maintain connections. The Oracle Net foundation layer uses Oracle protocol support that communicates with an industry-standard network protocol, such as TCP/IP, to communicate with the Oracle Database server.
Figure 1-14 illustrates the communication stack on the client.
The Oracle Database server side is similar to the client side as illustrated in Figure 1-15. A network protocol sends client request information to an Oracle protocol support layer, which then sends information to the Oracle Net foundation layer. The Oracle Net foundation layer then communicates with the Oracle Database server to process the client request.
TCP/IP with SSL
Oracle protocol support maps Oracle Net foundation layer functionality to industry-standard protocols used in client/server connections.
The one operation unique to the Oracle Database server side is the act of receiving the initial connection through Oracle Net Listener. The Oracle Net Listener, referred to in this document as the listener, brokers a client request, handing off the request to the server. The listener is configured with a protocol address. Clients configured with the same protocol address can send connection requests to the listener. When a connection is established, the client and Oracle server communicate directly with one another.
Figure 1-16 shows the listener accepting a connection request from a client and forwarding that request to an Oracle server.
See Also:Chapter 10, "Configuring and Administering Oracle Net Listener" for more information about the listener
Oracle Connection Manager is a software component that resides on its own computer, separate from a client or an Oracle Database server. It proxies and screens requests for the database server. In addition, it multiplexes database sessions.
In its session multiplexing role, Oracle Connection Manager funnels multiple sessions through a single transport protocol connection to a particular destination. In this way, Oracle Connection Manager reduces the demand on resources needed to maintain multiple sessions between two processes by enabling the Oracle Database server to use fewer connection end points for incoming requests.
As an access control filter, Oracle Connection Manager controls access to Oracle databases.
Oracle Net Services provides user interface tools and command-line utilities that enable you to easily configure, manage, and monitor the network.
Oracle Net Configuration Assistant enables you to configure listeners and naming methods.
Oracle Enterprise Manager combines configuration functionality across multiple file systems, along with listener administrative control to provide an integrated environment for configuring and managing Oracle Net Services.
Oracle Net Manager provides configuration functionality for an Oracle home on a local client or server host. With Oracle Enterprise Manager (Enterprise Manager) or Oracle Net Manager, you can fine-tune the listener and naming method configuration created with Oracle Net Configuration Assistant. In addition, Enterprise Manager and Oracle Net Manager offer built-in wizards and utilities that enable to you to test connectivity, migrate data from one naming method to another, and create additional network components.
Command-line control utilities enable you to configure, administer, and monitor network components, including listeners and Oracle Connection Managers.
Oracle Advanced Security is a separately licensable product that provides a comprehensive suite of security features for the Oracle environment. This suite of security features protects enterprise networks and securely extends corporate networks to the Internet. It provides a single source of integration with network encryption and authentication solutions, single sign-on services, and security protocols. Oracle Advanced Security integrates industry standards and delivers unparalleled security to the Oracle network and other networks.