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10 Replies Latest reply: May 6, 2008 4:46 AM by 634759 RSS

what is RAC

623584 Newbie
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RAC means one single physical database can be installed on more than one physical computer or server for balancing workload and backup data?

if yes, what kind company needs this? employees more than 10000?

can we also setup one single application on more than one computer? divide the application tier into components, and setup them on different computers?eg http on server A, form on server B, etc.....

data warehousing, data mining, are installed on database tier?
  • 1. Re: what is RAC
    dba-hyd Pro
    Currently Being Moderated
    Rac is for scalability, load balancing and high availabilitiy. You can initially start with a one node RAC and based on more workload and more number of users decide for adding more nodes. But in a single node RAC features of load balancing and high availability is not achieved hence you can start with minimum 2 node rac. Most of the production instances are 2 or 3 node racs.

    Yes, you can split the applications on different servers like concurrent managers on database tier, apache/forms/reports on another server.
  • 2. Re: what is RAC
    Hussein Sawwan-Oracle Employee ACE
    Currently Being Moderated
    RAC means one single physical database can be installed on more than one physical computer or server for balancing workload and backup data?
    RAC stands for Real Application Clusters. It allows multiple nodes in a clustered system to mount and open a single database that resides on shared disk storage. When a single system fail (node), the database service will still be available on the remaining nodes.

    A non-RAC database is only available on a single system. If that system fails, the database service will be down (single point of failure).
    if yes, what kind company needs this? employees more than 10000?
    It is not a matter of number of users as it is a matter of the availability of the database. If you cannot afford a single point of failure, then RAC should be taken into consideration.

    Oracle Real Application Clusters
    http://www.oracle.com/database/rac_home.html

    Note: 403347.1 - MAA Roadmap for the E-Business Suite
    https://metalink.oracle.com/metalink/plsql/ml2_documents.showDocument?p_database_id=NOT&p_id=403347.1
    can we also setup one single application on more than one computer? divide the application tier into components, and setup them on different computers?eg http on server A, form on server B, etc
    Yes, and this is called "Multi-node Installation".
  • 3. Re: what is RAC
    634759 Explorer
    Currently Being Moderated
    In addition to what has been said already:
    If your company cannot afford downtime longer than 15 minutes you should consider RAC. If they can, but still want some sort of high availability, you should consider clustering on the OS level (failover clustering, aka active/passive clustering). This means that when your server fails, the entire database will be transported to and started on another server in the cluster. Usually this can be achieved within 15 minutes nowadays. If you use solutions like HACMP (IBM), ServiceGuard (HP) or Sun Cluster, you can assign a hostname to the complete package of database and/or application, so there will be no need to run autoconfig and other tools to make things work again after a failover.
    Keep in mind that RAC makes your environment more complex, and therefore more sensitive to failure(s). It is a very nice solution nevertheless if you can handle/manage it.
    Arnoud
  • 4. Re: what is RAC
    mdtaylor Oracle ACE
    Currently Being Moderated
    It would be interesting to have EBS RAC customers indicate how many unplanned outages they had in the past year due to RAC/CRS crashes.
  • 5. Re: what is RAC
    623584 Newbie
    Currently Being Moderated
    Sami Malik,hsawwan,Arnoud Roth

    thanks for your explanation. now i know something about RAC.

    by the way, eg. if we set a RAC with two servers(A and B) to support database. for daily work, as default server A is in working mode and server B in standby mode, only when server A is down, server B will take over the place of A? can we setup both servers in working mode at same time for daily work?
  • 6. Re: what is RAC
    634759 Explorer
    Currently Being Moderated
    The whole idea of RAC is that it is active/active. This means that both (or all, if you have more than 2) servers will be active members of the cluster. All servers will be initially set up to working mode. There are ways of configuring your instances (e.g. through the use of services, or client-side connect definitions in tnsnames.ora) in such a way that one of the two, or not all servers will be accessed. You will let your client failover to the other instance in case of a failure. In this way, you would manually establish an active/passive environment.
    Remember though, that failover is performed on the client-side rather than the server side. In principle, both/all servers are up and running and ready to take connections, whether the clients use them or not.
    Arnoud
  • 7. Re: what is RAC
    634759 Explorer
    Currently Being Moderated
    It would be interesting to have EBS RAC customers indicate how many unplanned outages they had in the past year due to RAC/CRS crashes
    ...
    That is an interesting question! If you would ask me (I have been involved in several (very) large projects with E-Business Suite on RAC), I'd say quite a few. However, this is mainly due to the fact that many customers do not really understand their technology demands when it comes to RAC and cluster-related issues. This is often the root cause of many unexpected failures. That is why I am always advising customers to take on a technical architect with knowledge of cluster technology/RAC (like myself! haha!).
    Arnoud Roth
    Oracle E-Business Suite Technical Architect
    AMIS Services - The Netherlands
    http://www.amis.nl
    http://technology.amis.nl/blog
  • 8. Re: what is RAC
    Hussein Sawwan-Oracle Employee ACE
    Currently Being Moderated
    can we setup both servers in working mode at same time for daily work?
    Have a look at this link:

    Difference between "active-active" and "active-passive" configuration in RAC environments
    http://searchoracle.techtarget.com/expert/KnowledgebaseAnswer/0,289625,sid41_gci1006436,00.html
  • 9. Re: what is RAC
    RakeshTripathi Newbie
    Currently Being Moderated
    That's a good question !!

    My experience says that this tends to be more than what we have on a non-RAC environment - however, as Arnoud pointed out, if we dissect this to classify the root causes, this is predominantly on account of clusterware (Oracle/others) or hardware/network configuration issues and less on account of underlying reasons to do with Oracle Applications stack. Yes, for EBS to have a symbiotic relationship on the RAC infrastructure, it does take time to have all issues resolved on account of the underlying complexity - the degree of which may vary from implementation to implementation, though.

    Rgds,
    Rakesh
  • 10. Re: what is RAC
    634759 Explorer
    Currently Being Moderated
    So true, Rakesh! But still, too many times I see people blaming technology for their own incompetencies. Not that they are to blame, but if one doesn't know how to design, implement and manage a cluster, that is asking for trouble somewhere along the line. I see too many system admins, architects and consultants who think they know it all, and still implement faulty architectures... And then the technology is blamed for the instability it delivers.
    Arnoud