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Introduction

When setting up a client machine to connect to an Oracle database, you might encounter the TNS-03505: Failed to Resolve Name error despite having the correct configuration. This issue commonly occurs when the Oracle client cannot resolve the service name provided in the tnsnames.ora file. While the error message might seem confusing at first, it is usually caused by a small, easily fixable mistake in the configuration.

Understanding the TNS-03505 Error

The TNS-03505 error occurs when the Oracle client cannot find the database service name provided in the tnsnames.ora configuration file. This file contains the network addresses that help clients connect to databases. When the client cannot resolve the name specified, the connection attempt fails.

Example of the TNS-03505 Error:

C:\Users\localhost> tnsping orcl

TNS Ping Utility for 64-bit Windows: Version 11.2.0.1.0 - Production on 19-NOV-2014 15:22:45

Copyright (c) 1997, 2010, Oracle. All rights reserved.

Used parameter files:
C:\app\oracle\product\11.2.0\client_1\network\admin\sqlnet.ora

TNS-03505: Failed to resolve name
C:\Users\localhost>

This error message typically appears when trying to use the tnsping utility or when establishing a connection using SQL*Plus or other Oracle tools. Although the configuration file may appear correct, the issue may lie in minor but critical formatting issues, like leading or trailing spaces in the service name.

Troubleshooting and Resolving the Issue

Here are the steps to troubleshoot and resolve the TNS-03505 error:

Step 1: Check the tnsnames.ora File

The first thing to do is check the tnsnames.ora file to ensure that the service name is correctly defined. The file should look something like this:

orcl =
  (DESCRIPTION =
    (ADDRESS_LIST =
      (ADDRESS = (PROTOCOL = TCP)(HOST = localhost)(PORT = 1521))
    )
    (CONNECT_DATA =
      (SID = orcl)
    )
  )

In this example, the Oracle client is trying to resolve the orcl service name. It specifies the host, port, and SID (System Identifier) for the database.

Step 2: Remove Extra Spaces or Typos

A common mistake that leads to the TNS-03505 error is an extra space or incorrect character before the service name. Check for any unwanted spaces or formatting issues.

In my case, I discovered that there was an extra space in front of the orcl service name. Once I removed the extra space, the connection was successfully established.

Step 3: Verify the Service Name

If there are no issues with spaces or formatting, double-check that the service name (in this case, orcl) matches the correct service name defined in the listener.ora file on the server. If the names don’t match, you will need to update either the tnsnames.ora or the listener.ora to ensure consistency.

Confirming the Connection

Once the formatting issue is fixed, confirm the connection by using the tnsping utility again:

C:\Users\localhost> tnsping orcl

TNS Ping Utility for 64-bit Windows: Version 11.2.0.1.0 - Production on 19-NOV-2014 15:22:45

Copyright (c) 1997, 2010, Oracle. All rights reserved.

Used parameter files:
C:\app\oracle\product\11.2.0\client_1\network\admin\sqlnet.ora

OK (0 msec)
C:\Users\localhost>

As seen above, once the space was removed from the service name, the tnsping utility successfully returned an “OK” message, confirming that the connection was working.

Best Practices for Managing Oracle Configuration Files

• Check for Formatting Errors: Ensure there are no leading or trailing spaces in the service names or other critical configuration entries.
• Verify Service Names: Make sure the service name in the tnsnames.ora file matches the service name in the listener.ora and the database configuration.
• Use Consistent Naming: Use consistent naming conventions across all Oracle configuration files to avoid confusion.
• Test Configurations: Use tnsping and other Oracle utilities to test the connection after any changes to configuration files.

Conclusion

The TNS-03505: Failed to Resolve Name error can be easily resolved by checking for simple configuration mistakes, such as spaces or typos in the tnsnames.ora file. By following the steps outlined in this article, you can quickly troubleshoot and fix this error to ensure smooth connectivity to your Oracle database.