Hello,
The ORA-12170 error can occur for a number of reasons such as database down, listener down, bad sqlnet.ora parameter, network issues and firewall issues among others.
Please see: http://www.dba-oracle.com/t_ora_12170_tns_connect_timeout.htm
If the error occurred because of a slow network or system, reconfigure one or all of the parameters SQLNET.INBOUND_CONNECT_TIMEOUT, SQLNET.SEND_TIMEOUT, SQLNET.RECV_TIMEOUT in sqlnet.ora to larger values.