SCAN addresses can be used to specify the host and port for both the TNS listener and the ONS listener in the WebLogic console. A grid link data source containing SCAN addresses does not need to change if you add or remove RAC nodes. Contact your network administrator for appropriately configured SCAN URLs for your environment. For more information, refer to: http://www.oracle.com/technetwork/database/clustering/overview/scan-129069.pdf.