ORA-03135: connection lost contact

In my previous articles i have given detailed idea about multiple database and oracle errors. In this article i would like to give more information about the ORA-03135: connection lost contact error in detail. With this i would also like to give the resolution of this error. The error is most common error coming in the oracle and i need to explain it with detail.The ORA-03135 is an error that stems from the latter.

ORA-03135: connection lost contact – Why this error is coming?

In this section i would like to explain the actual cause of the error with the action we require to complete.

Cause of Error :

Cause 1 : Server unexpectedly terminated

The error itself is giving you the reason or cause of the error. The error is connection lost error. It simply means the server unexpectedly terminated or was forced to terminate and due to that the connection has lost. There are so many times this error will occur when we are working with complex set of tables.

Cause 2 : Server time out :

Multiple times we are getting the server time out error. The server time out error means when connection with network unexpectedly lost or server is timed out and request-reply mechanism is not working.This kind of error will occur due to some connectivity issues or may also be caused due to firewall while connecting through the remote environment.

Real Example for this cause :

While working on the oracle database there are many times the following error will occure. The error is coming at the time of connecting through the database.

ORA-03135: connection lost contact

Resolution of the Error :

We have already discussed about the cause of this error and now its time to discuss about the resolution of this specified error.

1.Server Session check :

The first check is always to check server session was terminated or not. There are multiple times due to any network connection issue the server session terminated.

How to check Server sessions ?

To check the server sessions you require to check the firewall connection first and then check with pinging the server.

Example :

If you want to check server session for Amit_Server then you can check with following command.

Ping Amit_server

You can check communication commands examples :

If reply is coming then the server connection is proper.

2.Check for timeout Parameters sqlnet.ora :

The second cause will be the sqlnet.ora timeout parameters. Most of the times the timeout parameters was set to less value. In that case we require to check and set the the sqlnet.ora timeout parameter properly to resolve this kind of error.

How to set timeout parameter in sqlnet.ora?

Location of file : $ORACLE_HOME/network/admin/.

1.The first step is to check the timeout parameters of sqlnet.ora. we need to check the value of expire_time parameters. Most of the time the parameter value is set to 0. So it could be always greater than zero.


2.There are other parameter also. If we found that the SQLNET.EXPIRE_TIME parameter set to some value and still error is coming then try to increase the value of that parameter and check again.


3.If still issue is there then kindly set sqlnet.inbound_connect_timeout and inbound_connect_timeout_listenername parameters to value 0.

3.Other checks :

We require to do some other checks to resolve this issue.

Check 1 : We require to check the NAT or Network Address Transition between client and server.

Check 2 : Checking firewall

We can do the checks for firewall for your local connections :

Windows XP -> Control panel -> security -> Tab “Advanced” 

I hope you got the clear idea about the ORA-03135: connection lost contact error in detail. If you like this article on ORA-03135: connection lost contact or if you have any issues with the same kindly comment in comments section.

2 Replies to “ORA-03135: connection lost contact”

  1. Thanks fort thé article on a production DB. I had previously applied all recommendations. I set sqlnet.expired_time=10, equally set the inbound
    inbound_connect_timeout_listenername to 0. Firewall is disabled yet I still have the error ora-03135

    1. Ohhh.. If you are facing the error still you need to check hardware to software connectivity in for connecting oracle…else kindly lock the ticket to Oracle for the same.

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