SCAN (Single Client Access Name) is a new concept introduced in 11gR2. SCAN helps to eliminate the use of Vitual IP(VIP) for the node failover.
Before 11gR2 we were using VIP, In the Grid Infrastructure when ever new node added or delete, entry of this node need to maintained in tnsnames.ora file accordingly.
But in 11gR2 Oracle created a listener running on top of the node listeners. This listener needs 3 SCAN IP's to be configured on the DNS
And it creates a virtual hostname which can be used as a signle entry in the tnsnames.ora
To Change the SCAN IP address it must be available and need to changes on the DNS by the network admin. So we have SCAN IP address available.
Steps:
1. To check the current status SCN IP address on DNS
$nslookup <scan-name>
$nslookup testrac-scan.abc.com
Server: 160.34.11.20
Address: 160.34.11.21#40
Name: testrac-scan.abc.com
Address: 160.34.11.88
Name: testrac-scan.abc.com
Address: 160.34.11.89
Name: testrac-scan.abc.com
Address: 160.34.11.90
2. Check the current status SCAN-VIP in the resource file
# $GRID_HOME/bin/srvctl config scan
SCAN name: testrac-scan, Network: 1/10.101.10.0/255.255.255.0/eth4
SCAN VIP name: scan1, IP: /testrac-scan.abc.com/160.34.11.88
SCAN VIP name: scan2, IP: /testrac-scan.abc.com/160.34.11.89
SCAN VIP name: scan3, IP: /testrac-scan.abc.com/160.34.11.90
3. Request network admin to update NEW SCAN IP address in the DNS server.
Example:
Old SCAN IP:
160.34.11.88
160.34.11.89
160.34.11.90
new SCAN IP:
170.35.12.60
170.35.12.61
170.35.12.62
$nslookup testrac-scan.abc.com
Server: 170.35.12.20
Address: 170.35.12.21#40
Name: testrac-scan.abc.com
Address: 170.35.12.60
Name: testrac-scan.abc.com
Address: 170.35.12.61
Name: testrac-scan.abc.com
Address: 170.35.12.62
4.CRS to update the SCAN VIP resources:
Note: current SCAN-VIP resource should be stopped before modifying the CRS resoruce file.
# $GRID_HOME/bin/srvctl stop scan_listener
# $GRID_HOME/bin/srvctl stop scan
# $GRID_HOME/bin/srvctl status scan
SCAN VIP scan1 is enabled
SCAN VIP scan1 is not running
SCAN VIP scan2 is enabled
SCAN VIP scan2 is not running
SCAN VIP scan3 is enabled
SCAN VIP scan3 is not running
# $GRID_HOME/bin/srvctl status scan_listener
SCAN Listener LISTENER_SCAN1 is enabled
SCAN listener LISTENER_SCAN1 is not running
SCAN Listener LISTENER_SCAN2 is enabled
SCAN listener LISTENER_SCAN2 is not running
SCAN Listener LISTENER_SCAN3 is enabled
SCAN listener LISTENER_SCAN3 is not running
# $GRID_HOME/bin/srvctl modify scan -n testrac-scan.abc.com
5. To verify that the change was successful
# $GRID_HOME/bin/srvctl config scan
SCAN name: sales-scan, Network: 1/1/10.101.10.0/255.255.255.0/eth4
SCAN VIP name: scan1, IP: /testrac-scan.abc.com/170.35.12.60
SCAN VIP name: scan2, IP: /testrac-scan.abc.com/170.35.12.61
SCAN VIP name: scan3, IP: /testrac-scan.abc.com/170.35.12.62
6. Start SCAN and the SCAN listener
# $GRID_HOME/bin/srvctl start scan
# $GRID_HOME/bin/srvctl start scan_listener