ORA-03135: Connection Lost Contact Tips

Question:  I am attempting to connect to my Oracle database and I get the ORA-03135 error:

ORA-03135: connection lost contact tips  

What can I do to avoid the ORA-03135 error?

Answer:  The oerr utility shows this for the ORA-03135 error:

ORA-03135: connection lost contact

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

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

The ORA-03135 error is common when connecting remotely when a firewall terminates the connection.  

One solution for the ORA-03135 error is to increase the value of the sqlnet.ora expire_time parameter in the sqlnet.ora file or to check for a expire parameter in a SQL*Plus profile.  

To diagnose the ORA-03135 error, start by checking to see if the OS PID still exists, using the ps –ef|grep syntax.

Check to see if there is a Network Address Translation (NAT) between the client and server

In Windows, check to see if a Windows firewall is checking for your local connections:

Windows XP -> Control panel -> security -> Tab "Advanced" 

Also, setting the parameters sqlnet.inbound_connect_timeout and inbound_connect_timeout_listenername to 0 can stop the ORA-03135 error.

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