Re: Regarding RAC vip failover and tnsnames entry

From: Riyaj Shamsudeen <>
Date: Mon, 11 May 2009 12:53:41 -0500
Message-ID: <>

Hi Sanjeev

>> Is it required to have second node entry in tnsnanames.ora for connection
to work
>> after vip failover.

Yes, you need to have second node entry also in your tnsnames.ora file.

You might want to understand what problems VIPs are resolving. Let's say that a new connection request is made and for some reason IP address in that tnsnames entry is not available and so, there is no response from that IP. Connection request will wait for TCP connect timeout parameters (typically 3-10 minutes controlled by tcp parameters), then try next entry in the tnsnames list.

By failing over VIP to surviving nodes of the cluster, there will be an immediate response, essentially as, 'no listener'. So, connection request will try next entry in the tnsnames entry immediately avoiding tcp connect timeout delays.

HTH Cheers

Riyaj Shamsudeen
Principal DBA,
Ora!nternals - Specialists in Performance, Recovery and EBS11i Blog:

On Mon, May 11, 2009 at 12:08 PM, Syed Jaffar Hussain <> wrote:

> Sanjeev,
> When a node fails, the VIP associated with failed node is automatically
> fail over to one of other nodes exists in the cluster.
> The existing connections will typically receive ORA-3113 errors and the new
> connections using address list will select the next entry in the list.
> On Mon, May 11, 2009 at 9:39 AM, sanjeev m <> wrote:
>> All,
>> We have two node RAC environment with the applications connections going
>> to first node.
>> (No reference to the second node in tnsnames.ora). We are not using load
>> balancing or failover.
>> If case of nic failure on first node CRS on the other node will failover
>> the vip (raising event and bringing up the resource online on second node)
>> and re-arp the machine address on the network.
>> Question:
>> (a) Existing connections: They will get an errors saying the instance is
>> down.
>> (b) New connections: They will be able to connect to vip on second node
>> (with reference to firsthostname-vip entry in tnsnames.ora).
>> Are both (a) and (b) true. Is it required to have second node entry in
>> tnsnanames.ora for connection to work after vip failover.
>> Regards
> --
> Best Regards,
> Syed Jaffar Hussain
> Oracle Certified Master (10g)
> Oracle ACE
> OCP 8i,9i & 10g DBA
> RAC Certified Expert
> Official Oracle RAC SIG Representative for Saudi Arabian region (
> I blog at
> --------------------
> "Winners don't do different things. They do things differently."

Received on Mon May 11 2009 - 12:53:41 CDT

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