Many Oracle DBAs, developers and just end-users often encounter an issue when they can not connect remotely to an Oracle database. There can be different reasons of the connection problems. I give below a short cookbook on resolving those database connection issues. But first let’s explore a bit Oracle connectivity concepts and terminology.
An Oracle database is represented to clients as a service; that is, the database performs work on behalf of clients. The service name is included in the connect data part of the connect descriptor. To connect to a database service, clients use a connect descriptor that provides the location of the database and the name of the database service. The address portion of the connect descriptor is actually the protocol address of the listener. To connect to a database service, clients first contact a listener process that typically resides on the database server. The listener receives incoming client connection requests and hands these requests to the database server. Once the connection is established, the client and database server communicate directly. Read more »