Resolving ORA-28040: No Matching Authentication Protocol with Oracle Database Connections

Introduction

When connecting to an Oracle database, especially newer versions like Oracle 12c, you may encounter the error ORA-28040: No matching authentication protocol. This issue typically arises due to compatibility problems between the JDBC driver and the version of the Oracle database server. The purpose of this tutorial is to guide you through resolving this error by understanding its causes and implementing effective solutions.

Understanding ORA-28040

The ORA-28040 error indicates that the client’s authentication protocol does not match any allowed protocols on the server. This mismatch often occurs when:

1. Outdated JDBC Drivers: Older JDBC drivers might use obsolete authentication mechanisms unsupported by newer Oracle database versions.
2. Incorrect SQLNET Configuration: Misconfiguration in the sqlnet.ora file can lead to incompatible logon versions being enforced.

Solutions

1. Upgrade JDBC Driver

To resolve compatibility issues, ensure you’re using a compatible version of the Oracle JDBC driver:

• For Oracle 12c and later, use ojdbc8.jar or higher.
• Avoid older drivers like ojdbc6.jar or ojdbc14.jar, as they may not support newer authentication protocols.

Example

Ensure your project’s build path includes the correct JDBC driver. In an IDE like Eclipse:

1. Right-click on your project in the Project Explorer.
2. Navigate to Build Path > Configure Build Path.
3. Under the Libraries tab, ensure ojdbc8.jar is listed and at the top if multiple drivers are present.

2. Configure SQLNET.ORA

Adjusting settings in your sqlnet.ora file can allow older clients to connect:

• Set SQLNET.ALLOWED_LOGON_VERSION_CLIENT and SQLNET.ALLOWED_LOGON_VERSION_SERVER to 8. This enables compatibility with older versions of JDBC drivers.

Example Configuration

SQLNET.ALLOWED_LOGON_VERSION_CLIENT=8
SQLNET.ALLOWED_LOGON_VERSION_SERVER=8

Place this configuration in the sqlnet.ora file, typically found under ORACLE_HOME/network/admin.

3. Reconfigure Passwords

If adjusting the above settings results in a "logon denied" error (ORA-01017), it may be necessary to recreate your database user’s password:

1. Connect to the Oracle database using SQL*Plus or another administrative tool.
2. Recreate the user and assign a new password.

Example SQL commands:

ALTER USER username IDENTIFIED BY new_password;

4. Adjust Build Path Order (Specific to IDEs like Eclipse)

If you’re using multiple JDBC drivers, ensure that there are no conflicts due to overlapping classes:

• In Eclipse, move the desired JDBC driver (ojdbc8.jar) to the top of your build path’s "Order and Export" tab.

Steps

1. Right-click on the project in Project Explorer.
2. Go to Build Path > Configure Build Path.
3. Navigate to the Order and Export tab.
4. Select ojdbc8.jar and click TOP to prioritize it.

Conclusion

By upgrading your JDBC driver, correctly configuring your sqlnet.ora, and managing your IDE’s build path, you can resolve the ORA-28040: No matching authentication protocol error effectively. These solutions ensure compatibility between client applications and Oracle database servers, enabling smooth connections and operations.