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11GR2 RAC - About SCAN with DNS

User_U66YKDec 16 2014 — edited Sep 6 2016

Hi Guys,

Just completed setup of 2 nodes RAC using Oracle VM Virtualbox for testing purpose.

I does not have a DNS so basically i make use of the /etc/hosts file as a work-around.

# SCAN

192.168.56.91    myrac-scan.localdomain   myrac-scan

192.168.56.92    myrac-scan.localdomain   myrac-scan

192.168.56.93    myrac-scan.localdomain   myrac-scan

Quite a few documents actually mentioned that if we use the hosts file to resolve SCAN name we can have only one SCAN IP address

I don't really understand what does it means. In my setup, i actually have 3 IPs and i don't see any issue with that.

In my client tnsnames.ora, i actually use the below. Either specify it as 91, 92 or 93, it will perform load balance. (either connect to rac1 or rac2)

RACDB =
    (DESCRIPTION = 
        (ADDRESS = (PROTOCOL = TCP)(HOST = 192.168.56.91)(PORT = 1521))
        (CONNECT_DATA =
            (SERVER = DEDICATED)
            (SERVICE_NAME = myracpoc.localdomain)
        )
    )

The below also shows i have 3 IPs. As i'm quite new to RAC, i'm trying to understand why documents mentioned that we should only have one ip in /etc/hosts instead of 3.

Appreciate your advise!

[oracle@myrac1 ~]$
$GRID_HOME/bin/srvctl config scan

SCAN name: myrac-scan.localdomain,
Network: 1/192.168.56.0/255.255.255.0/eth0

SCAN VIP name: scan1, IP:
/myrac-scan.localdomain/192.168.56.91

SCAN VIP name: scan2, IP:
/myrac-scan.localdomain/192.168.56.92

SCAN VIP name: scan3, IP:
/myrac-scan.localdomain/192.168.56.93

This post has been answered by oscrub on Dec 21 2014
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