[July 30, 2012 update: Corrected Note reference to 823586.1]
[Sept. 2, 2011 update: Our Maximum Availability Architecture architects have pointed out two additional considerations that are documented in our existing documentation: 1) Although SCAN listener is supported with EBS 12, if scan_name resolves in DNS to IP1 and IP2, the client-side 10.1.2 network code does not use round robin on the underlyng IPs if the first IP fails. An Autoconfig solution for this is being tracked through bug 10427234. The only existing workaround is to create custom TNS aliases configured with multiple SCAN IP addresses (Note 823587.1); 2) EBS does support use SCAN functionality, it cannot make complete use of the SCAN since the EBS clients are pre-11.2. For more details, see this Exadata whitepaper.]
Single Client Access Name (SCAN) is a new feature of Oracle Real Applications Clusters (RAC) 11g Release that provides a single name for the clients to access Oracle Database running in a cluster. The benefit of the SCAN Listener is that the client's connection data does not need to changed if you add or delete a node from a cluster.
The Single Client Access Name is configured during the installation of Oracle Grid Infrastructure. Once configured, application tier connection descriptors just specify the SCAN name rather than all the [virtual] hosts in the cluster.
Without the Single Client Access Name, the descriptor for a two-node cluster would be
VISION = (DESCRIPTION= (ADDRESS_LIST= (ADDRESS=(PROTOCOL=tcp)(HOST=C1-vip)(PORT=1521)) (ADDRESS=(PROTOCOL=tcp)(HOST=C2-vip)(PORT=1521))) (CONNECT_DATA=(SERVICE_NAME=VISION)))
With the Single Client Access Name, just the SCAN name needs to be specified:
VISION = (DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=C-SCAN)(PORT=1521))(CONNECT_DATA=(SERVICE_NAME=VISION)))
The benefit of the Single Client Access Name becomes apparent as the number of nodes in the cluster increases.
Which E-Business Suite releases can be used with SCAN Listeners?
You can configure E-Business Suite Release 11i and 12 environments to take advantage of Single Client Access Name functionality. The use of SCAN Listener is optional.
AutoConfig in E-Business Suite 11i does not support automated handling of SCAN Listeners. If you would like to use SCAN Listeners with EBS 11i environments, a manual setup process is described in:
AutoConfig in Oracle E-Business Suite Release 12 supports automated handling of SCAN Listeners. If you would like to use SCAN Listeners with EBS 12 environments, see: