Oracle 11g has a problem that is session timeout problem. You can add a row to sqlnet.ora file and listener.ora file to resolve session timeout problem.
sqlnet.ora
Note : Add this line to below of sqlnet.ora file.
INBOUND_CONNECT_TIMEOUT=3600
listener.ora
Note : Add this line to below of listener.ora file.
INBOUND_CONNECT_TIMEOUT_LISTENER=3600