ORA-03135: connection lost contact.

 This error appears when you are trying to connect to an oracle database and the connection receives time out. This ORA-03135 can be cause by the firewall.

In order to solve/avoid this kind of situation you have to modify the sqlnet.ora file. This file is located on $ORACLE_HOME/network/admin/sqlnet.ora.

One solution for the ORA-03135 error is to increase the value of thesqlnet.ora:expire_time parameter in the sqlnet.ora file :

SQLNET.INBOUND_CONNECT_TIMEOUT = 300
SQLNET.SEND_TIMEOUT = 300
SQLNET.RECV_TIMEOUT = 300

To check a solution for the ORA-03135 error, start by checking to see if the OS PID still exists, using the:

ps –ef|grep syntax

Thank you for reading this article.