Lesson 1

This module adds more depth to our prior discussion of Oracle Net Services architecture. We will look at the Oracle Net components and at all of the parameter files, including the

1. tnsnames.ora,
2. listener.ora,
3. protocol.ora, and
4. sqlnet.ora files.

We will also see how the pieces fit together and how Net uses these files to establish database communications.

• Learning Objectives: After completing this module, you will be able to:
  1. Describe the syntax and function of Net parameter files
  2. Define the components of Oracle network tools
  3. Describe the components and functions of the tnsnames.ora file
  4. Explain how the protocol.ora file operates
  5. Explain the purpose and uses of the sqlnet.ora file
  6. Establish Net communications at the process level
  7. Explain the purpose and syntax of Oracle database links
  8. Establish connections over database links
  We will begin the module by looking at the syntax and function of the net parameter files.

• Oracle Directory Naming: Allows clients to connect to a database by using information stored in a directory server that complies with LDAP, such as Active Directory.
• Oracle Names: An alternative to local or file-based name resolution methods. With Oracle Names, service names and addresses must be configured and maintained for each client. It was a product that stored connection information about all databases in a distributed environment in a single location. Any time an application issued a connection request, it would consult the Oracle Names repository to determine the location of the database server. Oracle Names was primarily an administrative aid that made the maintenance of information easier. Its use was not required and the alternative was to provide local tnsnames.ora files^[1]on every client machine.
• Oracle Unified Directory: Part of Oracle's directory solution, which offers identity management deployments. It provides storage, synchronization, proxy, and virtualization capabilities. Oracle Unified Directory (OUD) is a comprehensive directory service that centralizes user data and network resources, simplifying management and access control. It offers a unified platform for storing, managing, and accessing identity information, enabling efficient authentication and authorization. OUD supports large-scale deployments with high availability and performance, making it suitable for enterprise environments. It also provides features like data synchronization, proxy services, and virtualization to enhance flexibility and scalability.

Oracle utilizes those three key components to manage network communication for its database:

• Oracle Net Services: This is the overarching framework that provides the foundation for all network communication between clients and an Oracle database. It encompasses various components and protocols, including the Transparent Network Substrate (TNS).
• Transparent Network Substrate (TNS): This is the core protocol within Oracle Net Services responsible for establishing and maintaining connections between clients and the database server. It handles tasks like name resolution, connection establishment, and data transfer.
• Oracle Listener: This is a separate process that runs on the database server and "listens" for incoming client connection requests. It acts as an intermediary, directing those requests to the appropriate database instance.

While TNS is a crucial part of Oracle Net Services, it's not a completely separate component in the same way that Oracle Net Services and the Oracle Listener are. TNS is a protocol within the Oracle Net Services framework. Oracle Net Services is the overall system, TNS is the language they use to communicate, and the listener is the receptionist who directs calls.
While the interaction among these products does not generally require intervention beyond the initial installation, some customizations are often beneficial in an environment that is making heavy use of snapshots, symmetric replication, or other distributed functionality.

Oracle Net Services provides enterprise-wide connectivity solutions in distributed, heterogeneous computing environments^[2]. Oracle Net Services eases the complexities of network configuration and management, maximizes performance, and improves network diagnostic capabilities. This section introduces the basic networking concepts involved in a typical network configuration.

• Understanding Connectivity: Oracle Net, a component of "Oracle Net Services", enables a network session from a client application to an Oracle Database server. When a network session is established, Oracle Net acts as the data courier for both the client application and the database. It is responsible for establishing and maintaining the connection between the client application and database, 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.

[1] tnsnames.ora: The tnsnames.ora file in Oracle is a configuration file that stores network service names and their corresponding connection details. These details, known as connect descriptors, allow client applications to connect to specific Oracle databases by using a simple alias instead of the full database address.

[2] Heterogeneous computing environments: Heterogeneous computing environments in Oracle refer to systems that utilize a variety of different hardware and software components, like different operating systems or databases, within a single infrastructure. Oracle provides tools and technologies, such as Oracle Database Gateways and Heterogeneous Services, to seamlessly integrate and manage these diverse components, enabling data access and application interoperability across the heterogeneous environment.