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ORA-03135: connection lost contact

Cause:
1) Server unexpectedly terminated or was forced to terminate. .
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.

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

SQLNET.EXPIRE_TIME = 10

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.

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