Lesson 1

"Oracle Network Services" is bundled with the Oracle Database software in Oracle 23c. This holds for both 1) on-premises, 2) Oracle Cloud Infrastructure(OCI), or 3) a hybrid setup.
Oracle Network Services is an integral component of the database software installation, not a standalone product you install separately. During installation of Oracle Database 23c:

• Oracle automatically installs Oracle Net Listener (formerly "SQL*Net Listener")
• It also installs utilities like:
  • tnsnames.ora (client-side naming)
  • listener.ora (server-side listener configuration)
  • sqlnet.ora (network configuration rules)
• Plus server-side services:
  • Oracle Connection Manager (CMAN if selected)
  • Directory Naming (if using LDAP/OID) (optional)

In short:
✅ Oracle Database 23c ➔ ✅ Oracle Network Services installed automatically
There’s no separate install step for "Network Services" starting from Oracle 19c and onward including 23c.
You still use Oracle Network Services without having to install any type of additional servicesinside OCI environments.
Here’s the breakdown:

If you are installing in:	What's Needed
Oracle Cloud Infrastructure (OCI) Autonomous DB	No manual network service setup needed. Oracle automates secure listener, load balancing, and service endpoints (like regional and private endpoints).
OCI Virtual Machine (you control the DB server)	Oracle DB installer bundles Network Services automatically. You may need to configure your own listener.ora, tnsnames.ora, and Virtual Cloud Network (VCN) Security Lists/Rules.
On-Premises Database	Install Oracle Database normally. Oracle Network Services is part of the installed software. Manual configuration of listeners and client network files (tnsnames.ora) is expected.

In OCI Autonomous DB^[1], Oracle hides most low-level listener operations. In OCI IaaS (Infrastructure as a Service) (where you provision a VM manually), you are responsible for configuring the listener and network settings inside your DB VM.
In Oracle 19c and higher documentation and discussions, DB VM is generally understood to stand for database virtual machine. Oracle offers its database on virtual machines in various cloud and on-premises virtualization environments. When referring to these setups, "DB VM" is a common and accepted abbreviation for "database virtual machine." For example, in Oracle Cloud Infrastructure (OCI) documentation, you'll frequently see the term "VM DB System," which explicitly means a database system running on virtual machines. The "DB VM" part is a natural shorthand for this concept.
Diagram: Oracle 23c Network Services Installation Context

                 +-------------------+
                 | Oracle Database 23c|
                 +-------------------+
                          |
  +---------------------------------------------------+
  | Oracle Network Services Installed Automatically   |
  | - Oracle Net Listener                              |
  | - tnsnames.ora, listener.ora, sqlnet.ora           |
  | - Optional CMAN, LDAP Directory Naming             |
  +---------------------------------------------------+

Summary

Question	Answer
How to install Oracle Network Services 23c?	Already included with Oracle Database 23c install. No separate installation.
If OCI provides network services, is manual installation needed?	No. OCI manages networking at the infrastructure level. Only VM-based database servers need manual listener configuration.

What you should check as a DBA:
When you install Oracle 23c, after the installation always check:

• lsnrctl status → To verify the Listener is running.
• $ORACLE_HOME/network/admin → To verify that listener.ora, tnsnames.ora, and sqlnet.ora exist or are properly configured.

You will typically customize network behavior (e.g., SSL/TLS, load balancing) but not manually install Network Services separately.

The following is "Best Practices Checklist" for setting up Oracle Network Services after Oracle 23c database installation:

1. Listener Configuration
   • Run lsnrctl status to ensure the Listener is running.
   • Validate the default Listener is created at port 1521 (or a custom port if required).
   • Configure Dedicated Server or Shared Server mode explicitly in listener.ora if needed.
   • If SSL/TLS is required, set up TCPS protocol endpoints (listener-side and client-side).
   • Set INBOUND_CONNECT_TIMEOUT and CONNECT_TIMEOUT for network resilience.
2. Service Registration
   
   • Confirm the database instance automatically registers itself with the Listener (Dynamic Registration).
   • Verify LOCAL_LISTENER and REMOTE_LISTENER parameters in the database:
     • LOCAL_LISTENER = listener on the local machine
     • REMOTE_LISTENER = for RAC setups (Real Application Clusters) or remote nodes
   • Use ALTER SYSTEM REGISTER; if the database doesn't appear in lsnrctl services.
3. TNSNAMES Configuration
   • Edit tnsnames.ora properly at both server and client sides:
     • Include Service Names or SID as appropriate.
     • Prefer SERVICE_NAME over SID for newer databases.
   • Enable load balancing by specifying multiple hosts for connect strings if needed.
   
   Example connect string for load balancing:
   

   (DESCRIPTION=
     (LOAD_BALANCE=YES)
     (ADDRESS_LIST=
       (ADDRESS=(PROTOCOL=TCP)(HOST=host1)(PORT=1521))
       (ADDRESS=(PROTOCOL=TCP)(HOST=host2)(PORT=1521))
     )
     (CONNECT_DATA=(SERVICE_NAME=mydbservice))
   )
       

4. SQLNET Configuration
   • Define rules in sqlnet.ora:
     • Order of name resolution (e.g., NAMES.DIRECTORY_PATH=(TNSNAMES, EZCONNECT))
     • Encryption, Integrity settings if required (e.g., SQLNET.ENCRYPTION_CLIENT=REQUIRED)
   • Disable older insecure protocols (like TCP/IP without SSL) if security is a concern.
   • Enable Valid Node Checking if strict IP allowlists are needed (tcp.validnode_checking).
5. Firewall and Cloud Network Rules
   • Ensure firewall ports (default 1521) are open inbound to your database server (especially in OCI VCN setups).
   • For cloud deployments, configure OCI Security Lists or Network Security Groups (NSGs) to allow required traffic.
   • Restrict listener access only to trusted networks if possible.
6. High Availability (Optional)
   • Implement Listener Failover configurations if using Data Guard, RAC, or multi-node setups.
   • Configure Multiple Listeners (e.g., dedicated listeners for administration, Data Guard).
   • Consider using SCAN (Single Client Access Name) listeners in Oracle RAC setups.
7. Testing and Validation
   • Use tnsping servicename from the client to validate the TNS entries.
   • Test SQL connection manually:

     sqlplus username/password@servicename
             

   • Verify listener logs in $ORACLE_BASE/diag/tnslsnr/hostname/listener/trace/listener.log for any issues.
   • Enable listener tracing temporarily if diagnosing complex connection issues.

Summary Table

Area	Action
Listener	Confirm status, configure ports, optional SSL setup
Registration	Validate automatic registration (LOCAL_LISTENER, REMOTE_LISTENER)
TNSNAMES	Maintain accurate and load-balanced connect strings
SQLNET	Secure connection behavior (encryption, ordering)
Firewall/OCI Rules	Ensure correct inbound rules
High Availability	Setup failover listeners, SCAN if needed
Testing	TNSPING and SQL*Plus tests, check logs

Key Point:
Oracle Network Services in 23c are flexible but require careful configuration if you're optimizing for:

• High Availability (HA)
• Security (encryption/integrity)
• Performance (load balancing, connection pooling)
• Cloud Networking (OCI VCNs and NSGs)

This module discusses Oracle Net installation and configuration for Oracle databases 11g and higher.
This module does not cover the basic concepts of Net; you should already be familiar with the introductory Net content from the Network administration course. By the end of this module, you will be able to:

1. Describe changes to initialization parameters needed to support the new features
2. Add a network node in Net Assistant
3. Modify the tnsnames.ora file
4. Describe how to start a Net listener service with Oracle Enterprise Manager
5. Start a listener with line commands
6. Describe the uses of the Net Configuration Assistant

In the next lesson, we observe initialization parameters that involve new Net features.
Shared Oracle Databases
With Oracle databases shared across geographical areas, it is very important for the Oracle professional to recognize the importance of network communications on the performance of their databases. As you may know, Oracle provides for distributed communications between databases by using its (TNS) Transparent Network Substrate. The TNS is a distributed protocol that allows for transparent database communications between remote systems. The TNS acts as an insulator between Oracle's

1. logical request for data and
2. the physical communications

between the distributed servers. Because of this insulation between the Oracle logical data request and the internal workings of the network, much of the network performance tuning is in the hands of the network administrator. In other words, the Oracle administrator has very little direct control over the network configuration settings that can affect the overall performance of their database .

[1] OCI Autonomous DB: Within Oracle Cloud Infrastructure, OCI Autonomous Database represents a family of fully managed, self-driving, self-securing, and self-repairing database services optimized for specific workloads such as transaction processing and data warehousing, eliminating most manual database administration tasks. This serverless offering handles patching, backups, tuning, and upgrades automatically, allowing users to focus solely on their applications and data.