TNS-12535: TNS:operation timed out
 *Cause: The requested operation could not be completed within the time out
 period.
 *Action: Look at the documentation on the secondary errors for possible
 remedy. See SQLNET.LOG to find secondary error if not provided explicitly.
 Turn on tracing to gather more information.

TNS-00505: Operation timed out
 *Cause: The requested operation could not be completed within the timeout
 period.
 *Action: For further details, turn on tracing and reexecute the operation.

ORA-12170: TNS:Connect timeout occurred
 *Cause:  The server shut down because connection establishment or
 communication with a client failed to complete within the allotted time
 interval. This may be a result of network or system delays; or this may
 indicate that a malicious client is trying to cause a Denial of Service
 attack on the server.
 *Action: 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.
 If a malicious client is suspected, use the address in sqlnet.log to
 identify the source and restrict access. Note that logged addresses may
 not be reliable as they can be forged (e.g. in TCP/IP).