Error
Error Code: ORA-28545

Oracle ORA-28545: Net8 Agent Connection

📦 Oracle Database
📋

Description

The ORA-28545 error indicates a failure during connection initialization when using Heterogeneous Services to connect to a non-Oracle system or when calling an external procedure. This typically occurs due to configuration issues with Net8 or the agent itself.
💬

Error Message

ORA-28545: error diagnosed by Net8 when connecting to an agent
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Known Causes

4 known causes
⚠️
Incorrect TNS Configuration
The `tnsnames.ora` file contains incorrect or missing connection information for the Heterogeneous Services database link.
⚠️
Listener Configuration Issues
The `listener.ora` file is not properly configured to handle connections to the agent, preventing successful initialization.
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Agent Process Down
The agent process responsible for communicating with the non-Oracle system or external procedure is not running or is unresponsive.
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Network Connectivity Problems
There are network connectivity issues preventing the Oracle database from reaching the agent.
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Solutions

4 solutions available

1. Verify Listener Status and Configuration easy

Ensures the Oracle Net Listener is running and correctly configured to accept connections.

1
Log in to the Oracle database server where the listener is configured.
2
Check the status of the Oracle Net Listener. Replace `LISTENER_NAME` with the actual name of your listener (often 'LISTENER' by default).
lsnrctl status LISTENER_NAME
3
If the listener is not running, start it.
lsnrctl start LISTENER_NAME
4
Review the `listener.ora` file, typically located in `$ORACLE_HOME/network/admin/`. Ensure that the `HOST` and `PORT` parameters correctly reflect the network interface and port the listener is expected to be running on.
5
Verify that the service name or SID registered with the listener matches what is being used in the client's connection string (e.g., in `tnsnames.ora`). You can see registered services using `lsnrctl services LISTENER_NAME`.
lsnrctl services LISTENER_NAME

2. Validate Client TNSNAMES.ORA Configuration easy

Confirms that the client's `tnsnames.ora` file has the correct service name, host, and port information.

1
Locate the `tnsnames.ora` file on the client machine attempting to connect. This is typically found in `$ORACLE_HOME/network/admin/` or a custom location specified by the `TNS_ADMIN` environment variable.
2
Open the `tnsnames.ora` file in a text editor.
3
Find the TNS alias (service name) being used for the connection. Ensure the `HOST` and `PORT` values within that alias definition accurately point to the database server and the listener's port.
MYDB_ALIAS =
  (DESCRIPTION =
    (ADDRESS = (PROTOCOL = TCP)(HOST = your_db_host)(PORT = 1521))
    (CONNECT_DATA =
      (SERVER = DEDICATED)
      (SERVICE_NAME = your_service_name)
    )
  )
4
If using an SID instead of a SERVICE_NAME, ensure that is correctly specified and that the listener is configured to accept SID-based connections.
MYDB_ALIAS =
  (DESCRIPTION =
    (ADDRESS = (PROTOCOL = TCP)(HOST = your_db_host)(PORT = 1521))
    (CONNECT_DATA =
      (SID = your_sid)
    )
  )
5
Test the connection using `tnsping`. Replace `MYDB_ALIAS` with the TNS alias from your `tnsnames.ora` file.
tnsping MYDB_ALIAS

3. Check Network Connectivity and Firewalls medium

Verifies that the client can reach the database server on the specified listener port.

1
From the client machine where the error occurs, attempt to ping the database server's hostname or IP address.
ping your_db_host
2
Use a tool like `telnet` or `nc` (netcat) to test connectivity to the Oracle listener port (default 1521) on the database server. Replace `your_db_host` and `1521` as needed.
telnet your_db_host 1521
3
If `telnet` or `nc` fails to connect, it indicates a network issue. This could be due to a firewall blocking the port on the database server, an intermediary network device, or the client machine itself. Consult with your network administrators to ensure that TCP traffic on the listener port is allowed between the client and the database server.
4
On Linux/Unix, you might use `iptables` to check firewall rules. On Windows, check Windows Firewall settings.
sudo iptables -L | grep 1521

4. Investigate Oracle Net Services Configuration Files advanced

Performs a deep dive into `sqlnet.ora` on both client and server for misconfigurations.

1
Examine the `sqlnet.ora` file on the database server (typically in `$ORACLE_HOME/network/admin/`). Pay close attention to parameters like `NAMES.DIRECTORY_PATH`, `SQLNET.AUTHENTICATION_SERVICES`, and any security-related settings.
2
Similarly, review the `sqlnet.ora` file on the client machine. Ensure that `NAMES.DIRECTORY_PATH` includes `TNSNAMES` if you are using `tnsnames.ora` for resolution.
3
If you are using Oracle Internet Directory (OID) or other naming services, ensure that the relevant parameters in `sqlnet.ora` are correctly configured and that the naming service itself is accessible and functioning.
4
Check for any custom security configurations like `SQLNET.KERBEROS5_CONF` or `SQLNET.ENCRYPTION_SERVER`/`SQLNET.ENCRYPTION_CLIENT` that might be causing negotiation failures.
5
Temporarily disable certain security parameters (e.g., authentication methods) in `sqlnet.ora` on both client and server to isolate if a security configuration is the root cause. Remember to re-enable them after testing.