Configure the Shared Single Client Access Name (SCAN)
Single Client Access Name
In release 11g, SCAN is introduced, In SCAN act as cluster alias,
you does not need to change the client addresses when you need to change the public or virtual IP address as you add or remove nodes from cluster.
clients connecting to the SCAN no need to updated VIP addresses as nodes are added to or removed from the cluster.
SCAN listeners can run on any node in the cluster. SCANs provide location independence for the databases, so that client configuration
does not have to depend on which nodes run a particular database.
Shared Single Client Access Name
A shared single client access name (SCAN) enables you to share one set of SCAN virtual IPs (VIPs) and listeners on a dedicated cluster with other clusters.
Use of a shared SCAN enables multiple clusters to use a single common set of SCAN virtual IP (VIP) addresses instead of using multiple SCAN listerner.
Configure first on the server (i.e the cluster that hosts the shared SCAN), then on the client (the Oracle RAC cluster that will use this shared SCAN).
Example: If we configure 10 cluster then each cluster use 3 virtual ip for scan listener means total 3*10=30 virtual ip used. With Shared SCAN, we use only 3 Virtual IP
Configure the Shared SCAN
1. Login the cluster server where you create Shared SCAN listener.
2. Create a SCAN Cluster.
srvctl add scan_listener -clientcluster cluster_name
3. Create a new Oracle Notification Service (ONS) resource that is specific to the server cluster.
srvctl add ons -clientcluster cluster_name
4. Export the SCAN listener to the client cluster.
srvctl export scan_listener -clientcluster cluster_name -clientdata file_name
5. Export the ONS to client cluster.
srvctl export ons -clientcluster cluster_name -clientdata file_name
6. Set the environment variable.
ORACLE_CONFIG_HOME
TNS_ADMIN
7. Login to client cluster for configure the shared Scan listener.
8. Add the SCAN to the client cluster.
srvctl add scan -clientdata file_name
9. Create a SCAN listener that is exclusive to this client cluster.
srvctl add scan_listener -clientdata file_name
10. Create an ONS resource for this cluster.
srvctl add ons -clientdata file_name
