SCAN will be running on available nodes.
As we all know scan IP is for client failover, my question is , if suppose by some network issue, if node1, node2 and node 3 shutdown immediate.
What will happen to the client failover under this case??
It depend what failover you is taking about.
SCAN failover - If you have a bad lucky for tree SCAN IP was running at node1,node2 and node3 the scan will failover to survive node and for a minute (time to failover and pmon register database on scan listener) the client wich try connect will get ORA-12541 TNS :no listener.
If at least one SCAN IP is not on node1,node2 or node3 at moment of failure then no ORA-* is raised.
Client Failover - The client does not use SCAN to keep a session or to failover, the client use VIP to hold connection at database, all client of node1,node2 and node3 will failover or not depending your client configuration (i.e depend of Network Configuration TAF enabled or not).
First of all try to understand that SCAN is not bind to any node but whole Cluster along with SCAN listner and SCAN listener runs all the nodes in a cluster .
And this SCAN resolve the cluster not the node address in the cluster , that's why we can add,delete without changing the SCAN Address .
By default GRID set local_listener to local LISTENER and remote_listener to SCAN listener and this configuration help to connect with client , client connect first with scan listener and then with local listener and in the clusterware Database register itself with scan listener which allow them to take part in failover between the instances of the cluster .
You can check with srvctl status SCAN_LISTENER.
Shivendra Narain Nirala
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Scan is an integrated part of the cluster. It receives the connections from clients and passes over the connection to the local based on
- where is the service running
- which node is least loaded
Once the connection is passed over to the local listener the local listener then enables the client connection to the database. During this time if there is any failure of scan listener on a specific node then the scan would failover to the surviving node.
This would not affect the existing connections on the surviving node.
The connections on the failed instance or node would be failed over to the surviving node if server/client side TAF is enabled for the service/connection
All new connections would now be redirected by the scan running on the surviving nodes to the node listener of the surviving nodes based on the above mentioned condition
Vandana - Oracle