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8 Replies Latest reply: Dec 10, 2012 12:17 AM by 959717 RSS

RAC One Node: downtime after HW-outage?

vivalavida Journeyer
Currently Being Moderated
Hi ,
RAC One Node seems to be a good alternative compared to a "regular" RAC.
Since we don't have any experience with RAC One Node we are currently going through the available documentaion and try to get a picture of the advantages/disadvantages.
One major point is the question "what will exactly happen when an HW-failure or outage occurs?". It's my understanding - and what Oracle has documented - that the Oracle Clusterware provides failover protection to Oracle RAC One Node. If the node fails, Oracle Clusterware will automatically detect the failure and restart the Oracle RAC One Node database on another server in the pool.
In our case we would have the active node in Datacenter 1, the passive node in Datacenter 2. Therefore if the node in Datacenter 1 fails, the database should then get started on the node in Datacenter 2.

My questions now are:
- will that really automatically be done?
- what happens to the sessions which were connected to the database before the HW-failure?
- is it possible to determine how long this failover will take?

I'm sure that somebody has already tested this situation - any help will be appreciated.

Rgds
JH

Edited by: VivaLaVida on 05.12.2012 08:57
  • 1. Re: RAC One Node: downtime after HW-outage?
    JohnWatson Guru
    Currently Being Moderated
    If you need failover between data centres, you should probably be looking at Data Guard rather than any form of RAC.
  • 2. Re: RAC One Node: downtime after HW-outage?
    vivalavida Journeyer
    Currently Being Moderated
    Hi ,
    we will configure about over 10 instances on the RAC One Node - the box will have plenty of memory and enough CPU's. Therefore a RAC One Node will make more sense - at least from our point of view - as several standby databases. But this is not the point of this thread - let's take it as I described: failover will be done with RAC One Node.
    It would be great to get some answers to the questions I have asked.

    Many thanks & Rgds
    JH
  • 3. Re: RAC One Node: downtime after HW-outage?
    Levi-Pereira Guru
    Currently Being Moderated
    Hi,

    My questions now are:
    - will that really automatically be done?
    Yes, automatically and transparent
    - what happens to the sessions which were connected to the database before the HW-failure?
    Depend if you are using Omotion the connection will be redirected to another node, if you are cold failover the client will be have a short downtime.
    - is it possible to determine how long this failover will take?
    Depend of failure, but normal (could failover) is on range from 1 to 3 minutes, using (omotion- hot failover) no downtime.


    Read it :

    http://www.oracle.com/technetwork/products/clustering/overview/ug-raconenode-2009-130760.pdf?ssSourceSiteId=otncn

    Maybe this can clarify your issues.

    Any question just ask.

    Regards,
    Levi Pereira

    Edited by: Levi Pereira on Dec 5, 2012 11:58 AM

    PS: Ignore use of Omotion if you have "downtime after HW-outage". Consider only cold failover.
  • 4. Re: RAC One Node: downtime after HW-outage?
    vivalavida Journeyer
    Currently Being Moderated
    Hi Levi ,
    many thanks for your answers and the link - that certainly helps!

    Rgds
    JH
  • 5. Re: RAC One Node: downtime after HW-outage?
    JohnWatson Guru
    Currently Being Moderated
    Hello again. Are you under the impression that RAC One Node will move the database will move from one machine to another? It won't. The database will remain exactly where it is. All RAC One Node can do do is relocate the instance from one machine to another. Given that you mention two data centres, I doubt that this is what you need - unless you have a stretched cluster that clovers both data centres, and shared sdtorage visible on both sites.
  • 6. Re: RAC One Node: downtime after HW-outage?
    Levi-Pereira Guru
    Currently Being Moderated
    Little note:
    Oracle Clusterware will automatically detect the failure and restart the Oracle RAC One Node database on another server in the pool.
    In our case we would have the active node in Datacenter 1, the passive node in Datacenter 2.
    From info previously posted I considered he are using "Oracle Clusterware in Extended / Stretched Clusters".If not... there is no way to implement any RAC architecture.
  • 7. Re: RAC One Node: downtime after HW-outage?
    vivalavida Journeyer
    Currently Being Moderated
    Yes, we have shared storage - and the cluster itself will cover both nodes (DC1 and DC2).

    Rgds
    JH
  • 8. Re: RAC One Node: downtime after HW-outage?
    959717 Newbie
    Currently Being Moderated
    Ok ..It all depends on the bandwidth between the DC1 and DC2

    I have Rac one 1 Db on a 2 node active passive setup. I have seen instance swinging from node 1 to node 2 if the Node 1 fails. IF you want to swing the instance from DC1 to DC2 it will provide the Node 2 can reach the storage...I have seen the outage or session may hang for a minute or 2..Most of the timess sessions will be moved but it may break also......It protect says 95% orf session....

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