Features of the Connection Manager

Oracle Connection Manager (CMAN) is still used and supported in the Oracle RDBMS environment, including in modern versions such as Oracle 19c and 21c. CMAN remains relevant for tasks like connection concentration, network access control, and multiplexing connections to manage network traffic efficiently. CMAN helps reduce the overhead on the database server by pooling and multiplexing multiple client connections into fewer database connections. It's particularly beneficial in environments with a large number of users, such as cloud services or distributed systems. Some of its key features include:

• Connection Concentration: CMAN can consolidate many client connections into fewer physical connections to the database, which helps in reducing resource usage on the database server.
• Multiplexing: It allows multiple network sessions to share a single transport connection, which can reduce bandwidth consumption and improve performance in certain high-traffic environments.
• Access Control: CMAN can act as a gatekeeper for incoming connections, filtering traffic based on rules like IP addresses or user credentials.
• Firewall Capabilities: It adds an extra layer of security by enabling control over who can access the database.

These features make CMAN useful for managing large-scale Oracle deployments and optimizing network performance.

In the context of Oracle's cloud-enabled databases, the term "Oracle Net Services" is still widely used to refer to the networking technology that manages communication between clients and databases. This term is used for both on-premise and cloud environments. However, within Oracle Cloud Infrastructure (OCI)^[1] and Oracle Autonomous Databases, the networking features are often discussed using more modern cloud-specific terminology, such as Virtual Cloud Networks (VCNs)^[2], private endpoints^[3], Oracle Cloud Database Connectivity, and network security groups (NSGs)^[4]. These cloud-native networking solutions integrate with traditional Oracle Net Services but are specifically designed for the cloud environment's needs. While "Oracle Net Services" continues to play a fundamental role in managing network communication, including Transparent Network Substrate (TNS) configuration, cloud platforms introduce additional layers of connectivity management that complement traditional Oracle networking. For example:

• VCNs in OCI are used to define the network topology for cloud services.
• FastConnect or VPN services can securely connect on-premises environments to Oracle Cloud databases.
• Private Endpoints allow secure communication without exposing databases to the public internet.

In essence, Oracle Net Services is still relevant in cloud-enabled databases, but it's integrated with the broader cloud networking infrastructure.

Oracle Connection Manager enables you to take advantage of Oracle Network Services ability to multiplex or funnel multiple logical client sessions through a single transport connection to a multi-threaded server destination. This process is accomplished through Oracle Connection Manager's connection concentration feature. Concentration reduces the demand on the resources needed to maintain multiple connections between two processes. It enables the server to use fewer connection end points for incoming requests while increasing the total number of sessions that a server can handle. By using multiple Connection Managers, it is possible for thousands of concurrent users to connect to a server.

Unlike a SQL*Net or Net8 listener, which accepts connections from any remote host, Oracle Connection Manager includes a feature you can use to control client access to designated servers in a TCP/IP environment. In other words, you can direct the CMAN software to reject connections from unknown clients.
By specifying certain filtering rules, you may allow or restrict client access to a server based on the following criteria:

1. Source hostname or IP address for clients
2. Destination hostname or IP address for servers
3. Destination database server identifier

• Multiple Protocol Support Oracle Connection Manager also provides multiple protocol support enabling 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 in SQL*Net version 2. Net8 can traverse as many networking protocol stacks as can be installed and supported. In fact, the number of networking protocols supported is limited only by those restrictions imposed by the specific node;s hardware, memory, and operating system.
  Remember that CMAN is a new product within Oracle8 and it is intended to eventually replace the Net8 listener.

In the next lesson, you will find out how to configure the CMAN parameter file.

[1] Oracle Cloud Infrastructure (OCI): Oracle Cloud Infrastructure (OCI) is a comprehensive suite of cloud services offered by Oracle that provides on-demand access to compute, storage, networking, and various platform services. It enables businesses to build, deploy, and manage applications and workloads in a scalable, secure, and high-performance cloud environment.

[2] Virtual Cloud Networks (VCNs): Virtual Cloud Networks (VCNs) are software-defined networks that provide isolated and customizable network environments within a cloud provider's infrastructure. They allow you to segment and control your cloud resources, much like you would in a traditional on-premises data center.

[3] Private endpoints: Private endpoints are network interfaces that allow you to privately and securely connect to a service, effectively bringing that service into your own virtual network. This eliminates the need to expose your data to the public internet, enhancing security and control over your network traffic.

[4] Network security groups: Network security groups (NSGs) are a fundamental cloud network security feature that controls traffic flow to resources in a virtual network. They act like a virtual firewall, using rules to allow or deny inbound and outbound network traffic based on source, destination, port, and protocol.