All Oracle Error CodesOracle DBA Forum

NNC-00004:

connection is broken
Cause: The connection from a name server or client program to another server has been broken, either because that server has shut down, or because the network path to the server has stopped working. This error is usually displayed underneath an error which describes the problem in more detail.
Action: Make sure that the server being connected to is running and listening on the address used, and that there is network connectivity between the two end-points.