TNS-12535: How to Fix TNS Operation Timed Out Error


TNS-12535 errors, often referred to as Operation Timed Out errors, occur when a network connection has been established between a client computer and a server, but was unable to complete the connection in a timely fashion. This error is often associated with Oracle databases, but any application or protocol that uses a TCP/IP connection can return this error code.

When this happens, an Oracle Network Services (TNS) listener will throw the TNS-12535 error. In order to resolve this issue, further investigation is needed to identify the exact source and nature of the connection problem.


The most common cause of the TNS-12535 error is a misconfigured Oracle network environment. Incorrectly configured network names, client address, or incorrect port numbers can cause TNS-12535 errors.

Other causes include:

  • Firewall and/or router issues.
  • Problems with the client computer's TCP/IP stack.
  • A lack of free buffers or connections in the operating system of the server computer.
  • The Oracle server could also be down.


If you are seeing the TNS-12535 error code, it is likely that you are having an issue establishing a connection to your Oracle database. The steps below list basic troubleshooting tasks that should be undertaken to identify the cause of the problem.

Verify that your network ports and names are correctly defined in the tnsnames.ora, listener.ora, and sqlnet.ora files in the ORACLE_HOME folder, as well as in the clients TNS_ADMIN folder.

Check if the server computer is running and that the Oracle service is running on the server.

Check if there is sufficient disk space, RAM, and CPUs on the server computer.

Ping the server computer from the client computer to ensure the connection is working.

Check for any firewall or router issues that may be blocking the connection.

Restart the Oracle service on the server and the client computer.

  1. Try to open a socket connection from the client computer to the server.

Once the source of the problem is identified, the appropriate next steps can be taken to address the issue.


Q: What does a TNS-12535 error indicate?

A: A TNS-12535 error indicates that an Oracle network connection was unable to complete in a timely fashion.

Q: What are the most common causes of the TNS-12535 error?

A: The most common causes are misconfigured network configurations, firewall or router issues, a lack of resources in the operating system, or a problem with the Oracle server itself.

Q: What are the steps to troubleshoot a TNS-12535 error?

A: The steps to troubleshoot a TNS-12535 error include verifying network port and name definitions, checking server and Oracle service status, ensuring sufficient disk space, RAM, and CPUs, pinging the server from the client, checking for and resolving any firewall or router issues, and restarting the Oracle service.


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