Summary

You need to understand several key components in order to succeed when networking in an Oracle environment. The main responsibilities of the DBA include determining the applications and type of connections that will be supported, the number of users and the locations from which they will be accessing the network, and the security issues involved in protecting sensitive information, such as single sign-on and data encryption.

In addition, you need to choose from the three basic types of network configurations when setting up an Oracle network: single-tier architecture, two-tier architecture, and n-tier architecture. Because systems have evolved from the simpler single-tier architecture to the more complex n-tier architecture, which can include connections through middle-tier servers and the Internet, you will most likely choose between the two architectures that Oracle Net is an integral part of: two-tier or n-tier.

Oracle Net manages the flow of information from client computers to Oracle servers and forms the foundation of all networked computing in the Oracle environment. Oracle Net provides services that can be divided into five main categories: connectivity, directory services, scalability, security, and accessibility. Connectivity solutions include support for multiple protocols, multiple operating systems, and Java and Internet. Directory services provide an infrastructure to resolve Oracle service names through a centralized naming repository. Scalability solutions include Connection Manager and Oracle Shared Server. Security options include Oracle Advanced Security, which provides an additional layer of security options and robust support for many varieties of firewalls. Accessibility support includes Heterogeneous Services and support for calling external procedures. Oracle Net also provides connectivity to Java stored procedures and URL connections.

The listener is the main server-side component in the Oracle Net environment. Listener configuration information is stored in the listener.ora file, and you manage the listener using the lsnrctl command-line utility. You configure the listener by using the Oracle Net Manager. The Oracle Net Manager provides a graphical interface for creating most of the Oracle Net files that you will use for Oracle, including the listener.ora file. If multiple listeners are configured, each one has a separate entry in the listener.ora file.

Oracle10g provides a feature called dynamic service registration. This feature allows an Oracle instance to automatically register itself with a listener. The listener must be configured with TCP/IP and listen on port 1521, or you must specify the parameter LOCAL_LISTENER in the init.ora file. You must set the parameters INSTANCE_NAME and SERVICE_NAMES in the init.ora file for the Oracle instance to enable dynamic service registration.

You can configure logging and tracing on the Oracle server using Oracle Net Manager, Oracle Enterprise Manager, or the lsnrctl utility. Logging records significant events, such as starting and stopping the listener, along with certain kinds of network errors. Errors are generated in the log in the form of an error stack. Tracing records all events that occur even when an error does not happen. The trace file provides a great deal of information that logs do not.Tracing uses much more space than logging and can also have an impact on system performance.Enable tracing only if other methods of troubleshooting fail to resolve the problem.

Configuring the Oracle server components correctly is the first step to successfully implementing Oracle in a network environment. If you do not have the Oracle server network components configured correctly, you will be unable to provide connection support to clients in the Oracle environment. Configure and test the server network components before configuring the Oracle clients.

Depending on your network environment, the client configuration setups can vary from no work to configuring a number of files on the client. The names resolution methods available for clients include hostnaming, Oracle Easy Connect, localnaming, Oracle Internet Directory, and External Naming. Hostnaming, which can only be used if you are using TCP/IP, is mainly used for simple Oracle networks. Oracle Easy Connect is an extension of hostnaming and allows for the inclusion of additional information such as the hostname and port specification. Localnaming is the most popular of the names resolution methods, and it uses the tnsnames.ora file, which is typically located on each client, to resolve net service names. The client looks up the net service name in the tnsnames.ora file and uses the resulting connect descriptor information to connect to the Oracle server. The hostnaming and localnaming methods are configured using the Oracle Net Manager or Oracle Enterprise Manager. Oracle Internet Directory is a Lightweight Directory Access Protocol (LDAP)–compliant server that provides for centralized management of Oracle database connection identifier information. External Naming uses a non-Oracle facility, such as DNS, to manage and resolve Oracle service names.

It is important to know how to troubleshoot connection problems. You should know the general format and content of the tnsnames.ora and sqlnet.ora files to be able to identify syntax errors. You should know where these files reside on the client. You should understand how the various names resolution methods work. You should become familiar with the tools that can be used, such as the TCP/IP-supplied ping utility and the Oracle-supplied tnsping utility to assist you when troubleshooting these problems. Finally, you should familiarize yourself with the most common Oracle error messages that can occur as a result of connection problems.

This chapter provides the foundation of knowledge that you will need when you are designing, configuring, and managing the Oracle network infrastructure. The decisions you make about the network design have ramifications in terms of the scalability, security, and flexibility of your Oracle environment. When you understand the underlying network architecture, network options available to you, and how to configure and manage the Oracle Net infrastructure, you will be able to provide consistent and reliable connections to Oracle services for your clients.

Exam Essentials

Know the database administrator’s responsibilities and how they relate to network administration. Be able to list the responsibilities of the database administrator with respect to network administration. Can you define the basic network configuration choices and summarize the strengths and weaknesses of these options?

Understand what Oracle Net is and the functionality it provides. Be able to list the five categories of functionality that Oracle Net provides and explain the functionality that falls into each category. Also understand what functionality the Oracle Shared Server and Oracle Connection Manager options provide. In addition, be able to define Oracle Advanced Security and know when to use it.

Be familiar with Oracle’s Internet connection options. Have a basic understanding of the connection options that Oracle provides from the Internet. This includes connections made via an application server and connections made directly to the Oracle server from a web browser.

Be able to define the main responsibilities of the Oracle listener. To fully understand the function of the Oracle listener, you should understand how the listener responds to client connection requests. In addition, know the difference between bequeath connections and redirect connections, and know under what circumstances the listener will use each. Also, be able to outline the steps involved in using each of these connection types.

Be able to define the listener.ora file and the ways in which the file is created. To understand the purpose of this file, know its default contents and how to change the file using the various Oracle tools. In addition, be able to define the sections of the file and know the definitions of the optional parameters it contains. Also understand the structure of the listener.ora file when one or more listeners are configured.

Understand how to use the lsnrctl command-line utility. To start up and shut down the listener, know how to use the lsnrctl command-line utility. Be able to explain the command-line options for the lsnrctl utility, such as services, status, and reload. When using this utility, also know the options available to you, and be able to define the various set commands.

Understand the concepts of static and dynamic service registration. Be able to define the difference between static service registration and dynamic service registration and know the advantages of using dynamic service registration over static service registration. Also, be aware of the situations in which you have to use static service registration. Lastly, be familiar with the init.ora parameters that you will need to set in order to enable dynamic service registration. Be able to diagnose and correct network connectivity problems. Know the types of serverside errors that can occur and how to diagnose and correct these problems. Be able to define the difference between logging and tracing and know how to use the types of packet information that you may find in a trace file.

Define the Oracle client-side names resolution options. Be able to define the Oracle clientside names resolution options. Know in which situations to use localnaming, Oracle Easy Connect Naming, hostnaming, and OID.

Define the prerequisites for using the hostnaming method. Know how to configure this method using the Oracle Net Manager, and understand the connection process when you use this method. You also need to be able to define the parameter that you may have to add to the listener.ora file. In addition, understand the HOSTS file.

Use the Oracle tools to configure the client. Be able to use various Oracle tools to configure the sqlnet.ora file on the client. Understand the meaning of the NAMES.DEFAULT_DOMAIN and NAMES.DIRECTORY_PATH parameters within the sqlnet.ora file.

Define the localnaming method. In addition to knowing the meaning of the localnaming method and what it does, understand how to use the Oracle Net Manager to configure this names resolution method. Understand the primary file used in the localnaming method, the tnsnames.ora file.

Define the contents and structure of the tnsnames.ora file. Be able to describe the tnsnames.ora file and the various sections of the file and to explain how the file is used.

Understand the contents of the tnsnames.ora file so that you can identify syntax problems with the structure of entries in the file. Be familiar with the common locations of this file and how to set the TNS_ADMIN parameter to override the default location of this and the other client-side network files.

Define and correct client-side errors. Understand the types of client-side connection errors that can occur. Be able to define these errors and understand the situations in which a client might encounter them.

----------------------------------

listener.ora   tnsnames.ora   sqlnet.ora   init.ora