1. Single client access name (SCAN) is the virtual hostname to provide for all clients connecting to the cluster (as opposed to the vip hostnames in 10g and 11gR1).
2. SCAN is a domain name registered to at least one and up to three IP addresses, either in the domain name service (DNS) or the Grid Naming Service (GNS).
3. By default, the name used as the SCAN is also the name of the cluster and must be globally unique throughout your enterprise. The default value for the SCAN is based on the local node name. SCAN name must be at least one character long and no more than 15 characters in length, must be alphanumeric - cannot begin with a numeral and may contain hyphens (-). If you require a SCAN that is longer than 15 characters, then select an Advanced installation.
4. SCAN VIP addresses must be on the same subnet as virtual IP addresses and public IP addresses.
5. Oracle strongly recommends that you do not configure SCAN VIP addresses in the hosts file. But if you use the hosts file to resolve SCAN name, you can have only one SCAN IP address.
6. Oracle recommends using 3 SCAN listeners for RAC. If the RAC has 3 nodes, each node will have its own SCAN listener. If there is only 1 SCAN listener configured, then only 1 node would have the SCAN Listener running.

Status of SCAN IP

grid@rac1 ~]$ srvctl status scan
SCAN VIP scan1 is enabled
SCAN VIP scan1 is running on node rac2

Status of SCAN Listener

[grid@rac1 ~]$ srvctl status scan_listener
SCAN Listener LISTENER_SCAN1 is enabled
SCAN listener LISTENER_SCAN1 is running on node rac2

Configure SCAN IP

[grid@rac1 ~]$ srvctl config scan
SCAN name: rac-scan, Network: 1/192.168.2.0/255.255.255.0/eth0
SCAN VIP name: scan1, IP: /rac-scan.localdomain/192.168.2.201

Configure SCAN Listener

[grid@rac1 ~]$ srvctl config scan_listener
SCAN Listener LISTENER_SCAN1 exists. Port: TCP:1521

Display the entries in etc host file

[grid@rac1 ~]$ more /etc/hosts
# Public
192.168.2.101 rac1.localdomain rac1
192.168.2.102 rac2.localdomain rac2
# Private
192.168.0.101 rac1-priv.localdomain rac1-priv
192.168.0.102 rac2-priv.localdomain rac2-priv
# Virtual
192.168.2.111 rac1-vip.localdomain rac1-vip
192.168.2.112 rac2-vip.localdomain rac2-vip
# SCAN
192.168.2.201 rac-scan.localdomain rac-scan

[grid@rac1 ~]$
Validating SCAN on second Node
[grid@rac2 ~]$ srvctl status scan
SCAN VIP scan1 is enabled
SCAN VIP scan1 is running on node rac2
[grid@rac2 ~]$ srvctl status scan_listener
SCAN Listener LISTENER_SCAN1 is enabled
SCAN listener LISTENER_SCAN1 is running on node rac2
[grid@rac2 ~]$ srvctl config scan
SCAN name: rac-scan, Network: 1/192.168.2.0/255.255.255.0/eth0
SCAN VIP name: scan1, IP: /rac-scan.localdomain/192.168.2.201
[grid@rac2 ~]$ srvctl config scan_listener
SCAN Listener LISTENER_SCAN1 exists. Port: TCP:1521

Stop SCAN and SCAN_LISTENER

[grid@rac1 ~]$ srvctl stop scan_listener
[grid@rac1 ~]$ srvctl stop scan
[grid@rac1 ~]$ srvctl status scan
SCAN VIP scan1 is enabled
SCAN VIP scan1 is not running
[grid@rac1 ~]$ srvctl status scan_listener
SCAN Listener LISTENER_SCAN1 is enabled
SCAN listener LISTENER_SCAN1 is not running
[grid@rac1 ~]$ srvctl config scan
SCAN name: rac-scan, Network: 1/192.168.2.0/255.255.255.0/eth0
SCAN VIP name: scan1, IP: /rac-scan.localdomain/192.168.2.201
[grid@rac1 ~]$ srvctl config scan_listener
SCAN Listener LISTENER_SCAN1 exists. Port: TCP:1521
[grid@rac1 ~]$

Restarting SCAN and SCAN_LISTENER

[root@rac1 ~]# srvctl start scan
[root@rac1 ~]# srvctl start scan_listener

References
11gR2 Grid Infrastructure Single Client Access Name (SCAN) Explained [ID 887522.1]

posted by Jaswinder Singh @ 9:00 AM

0 Comments: