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11g R2 SCAN [message #458463] Sun, 30 May 2010 11:34 Go to next message
Messages: 295
Registered: May 2007
Senior Member
Hi All,

Just wanted to get a little on 11gR2 SCAN . I was reading the doc'n which clearly says that

" SCAN is configured at a cluster level not at the node level, that's what makes it so flexible -- no mater how many nodes your clusters consists of, your clients can continue to use SCAN to access the services of your cluster utilizing all nodes even if you add or delete them.

The SCAN is a virtual IP name, similar to the names used for virtual IP addresses, such as node1-vip. However, unlike a virtual IP, the SCAN is associated with the entire cluster, rather than an individual node, and associated with multiple IP addresses, not just one address."

Please find the attached listener.ora which has the SCAN entries and /etc/hosts file all the 3 IP's(public,private and VIP) of all the nodes .

If we are using SCAN then why are having all the 3 IP's. To my understanding SCAN eliminates to enter the IP addresses at the node level , but in my case we are configuring 3 IP's in the /etc/hosts file on each server. It should be only the SCAN IP addresses .

Please correct me if I'm wrong somewhere and kindly clear my confusion on SCAN IP.

  • Attachment: hosts.txt
    (Size: 1.18KB, Downloaded 1070 times)
Re: 11g R2 SCAN [message #458471 is a reply to message #458463] Sun, 30 May 2010 13:30 Go to previous message
John Watson
Messages: 8807
Registered: January 2010
Location: Global Village
Senior Member
I did post a blog entry on this topic, at http://www.orafaq.com/node/2369 do you think you could have a look and tell me if it is helpful?
As far as I can tell from your hosts file, you aren't using DHCP and GNS. So, yes, you will need those entries in /etc/hosts or your DNS. Since you have two SCAN listeners on one node, I guess you have a two node cluster, and the other node is currently hosting the third SCAN listener? Are they on DHCP assigned VIPs, or on static VIPs? How do you resolve the SCAN listening address? Do you have a DNS that load balances between the three SCAN listeners?
It looks a bit confused at the moment - as though you are using partly static addresses, and partly dynamic.
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