ORA-03135: connection lost contact

1) Server unexpectedly terminated or was forced to terminate. .
2) Server timed out the connection

1) Check if the server session was terminated.
2) Check if the timeout parameters are set properly in sqlnet.ora.

ORA-03135 occurs when we try to connect oracle database and the connection gets time out. ORA-03135 can also be caused by the firewall when connecting remotely.

To resolve ORA-03135 exception we need to increase the value of the expire_time parameter in the SQLNET.ORA file, as mentioned in Action part. We can also set the parameters sqlnet.inbound_connect_timeout and inbound_connect_timeout_listenername to 0 can avoid the ORA-03135 error. SQLNET.ORA file is located under $ORACLE_HOME/network/admin/.

We recently faced ORA-03135 on one of our testing environment after Server Admin team did a firewall upgrade. Users were able connect to the database, but if their session was idle for some time, the connection was getting terminated.

To resolve ORA-03135 we added following to SQLNET.ORA file


This keeps connections alive by send a check to verify that client/server connections are active in every 10 minutes. If the probe finds a terminated connection, or a connection that is no longer in use, then it returns an error, causing the server process to exit.

Follow me

Contact us for Training/ Job Support

Caution: Your use of any information or materials on this website is entirely at your own risk. It is provided for educational purposes only. It has been tested internally, however, we do not guarantee that it will work for you. Ensure that you run it in your test environment before using.