VI identifies a listener protocol address by a discriminator number. The discriminator number is similar to the TCP/IP port..
Host Name
Enter the host name of the computer where the listener resides.
Use the standard discriminator number of 1521
Select this option to if the listener is configured to receive requests at discriminator number of 1521.1521 will not conflict with the TCP/IP port number 1521.
Use another discriminator number
Select this option to specify another discriminator number other than 1521. Ensure that the listener was configured for this discriminator number as well.