Instant Client:

http://www.oracle.com/technology/tech/oci/instantclient/index.html

Easy Connect:


Specifying a Connection by Using the Easy Connect Naming Method
You can specify a connection address to an Oracle Database directly from a client application, without having to configure a tnsnames setting for the Instant Client. This method is convenient in that you do not have to create and manage a tnsnames.ora file. However, your application users will need to specify the host name and port number when they want to log in to your application.

For example, suppose you are running SQL*Plus on the client machine and want to connect to the sales_us database, which is located on a server whose host name is shobeen and port number is 1521. If you launch SQL*Plus from the command line, you could log in as follows:

Enter user-name: system/admin@//shobeen:1521/sales_us

Similarly, in your application code, you can use Oracle Call Interface net naming methods to create the Instant Client-to-Oracle Database connection. For example, the following formats in the OCIServerAttach() call specify the connection information:

Specify a SQL connect URL string using the following format:

//host[:port][/service_name]

For example:

//shobeen:1521/sales_us

Alternatively, you can specify the SQL connect information as an Oracle Net keyword-value pair. For example:

"(DESCRIPTION=(ADDRESS=(PROTOCOL=tcp) (HOST=shobeen) (PORT=1521))(CONNECT_DATA=(SERVICE_NAME=sales_us)))"