When should a VIP address move to other node? 2006-02-10 - By Alexei_Roudnev
If VIP is used just to speed up switchover (as you describe), than of course
it all is correct, but it is a very strange method to have such result (app.
can just connect to both nodes and use one which response first).
And it all require very careful configuration, because listener listens on
0.0.0.0 in most cases (and many DBA configure it by these way, for
reliability).
PS. You can have NIC failures, switch failure, and many other cases of
failures in real world, so these VIP transitions are not very useful anyway.
The only _reliable_ method of connections is _connect to all nodes, and use
keepalives in BOTH directions_. All other methods of failover or failure
detections have many scenarios when they do not work at all (and it confirms
by my tests).
-- -- Original Message -- --
From: <CLEMENS.BLEILE@(protected)>
To: "Alexei_Roudnev" <Alexei_Roudnev@(protected)>; "Silviu Marin-Caea"
<silviu_marin-caea@(protected)>; <suse-oracle@(protected)>
Cc: <clemens.bleile@(protected)>
Sent: Friday, February 10, 2006 2:56 AM
Subject: AW: Re: Re: [suse-oracle] When should a VIP address move to other
node?
>
> Hi Alexei,
>
> I think there is a misunderstanding here. A service shouldn't depend on a
failed-over VIP.
>
> Let's take an example of a 2-node RAC:
>
> A node crashes and the VIP starts on the other node. CRS activates the
services on the other node as well, but it registers them under the listener
of the local VIP (ie the VIP of the surviving node). If a client connects to
the VIP of the failed node it gets an error back immediately (ORA-12541 (See ORA-12541.ora-code.com) no
listener) and tries to connect to the next VIP in the address-list of your
tnsnames.ora and succeeds to connect. I.e. a VIP running on a different node
than it should returns an error. The important thing is that it returns the
error immediately and the client can handle it immediately (e.g. with TAF).
>
> If the second node comes back then services remain on the node which
didn't crash (if you have configured the service "Preferred/Available").
When the VIP switches back you may have a short "unavailability" to connect
to the service (only to connect, not already "connected" sessions). On my
Laptop with vmware this was 12 seconds. In a real environment probably less.
After the failed node finished to boot I relocated the services back. This
was another "unavailability" of service of 1 second. I started a test on my
Laptop with 1 node up and running. To bring the service on the "down node"
up again resulted in an unavailability of service of 13 seconds to connect
to the service.
>
> Could you please explain where your long wait times come from?
>
> My understanding is that VIPs are there only for NIC-failures (i.e. a node
crash means also a NIC failure ;-)). If a NIC failes then the VIP starts on
another node and returns errors immediately when trying to connect to Oracle
using this VIP.
>
> Ciao
>
> Clemens
>
>
>
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