4 Replies Latest reply: Apr 9, 2012 3:03 AM by Vijay.Cherukuri-Oracle RSS

    If all SCAN listeners fails

    Vijay.Cherukuri-Oracle
      Hi Experts,

      AFIK SCAN listeners re-directs the all incoming client connections to local listeners.

      if one SCAN fails the SCAN o failure node fail over to other live nodes

      What happens if all the SCAN listeners fails AT SAME TIME . (Just imagine)

      Are the incoming connections fails till services restored or other possible way ?


      --
      Thanks in Advance
      Vijay
        • 1. Re: If all SCAN listeners fails
          912595
          887400 wrote:
          Hi Experts,

          AFIK SCAN listeners re-directs the all incoming client connections to local listeners.

          if one SCAN fails the SCAN o failure node fail over to other live nodes

          What happens if all the SCAN listeners fails AT SAME TIME . (Just imagine)

          Are the incoming connections fails till services restored or other possible way ?


          --
          Thanks in Advance
          Vijay
          Tell us in what condition all scan listener will fail?
          If you ask this question to yourself you probably will find the answer :)

          SCAN ips are registered in DNS or GNS but SCAN Listener are the clusterware resources. So when node is down, and if SCAN listener was running on this node then SCAN listener is failover to other available node.
          So the possibility of all SCAN listener will occur in case when all nodes are down and there is no Clusterware alive on any node to failover to.

          But yes if you explicitly kills all scan listener then the possibility is not to accept the clients connections, but again when you kill it, it'll again failover to other node :)

          Have a look - >http://www.oracle.com/technetwork/database/clustering/overview/scan-129069.pdf
          • 2. Re: If all SCAN listeners fails
            Vijay.Cherukuri-Oracle
            Hi,

            While reading that SCAN paper i got that question.

            OK now.

            Let say. i have 2node RAC by default has 3 SCAN listeners

            Node 1 has 2 SCAN listeners and Node 2 has One.

            If the node 1 fails then SCAN listeners on that node will fail over to node 2 .

            Now node2 hosts all three SCAN listeners .When the NODE 1 comes back the 2 SCAN listeners will fail back to node 1 .


            Please correct me if I am wrong.

            --Thanks
            Vijay

            Edited by: 887400 on Apr 9, 2012 12:08 AM
            • 3. Re: If all SCAN listeners fails
              912595
              887400 wrote:
              Hi,

              While reading that SCAN paper i got that question.

              OK now.

              Let say. i have 2node RAC by default has 3 SCAN listeners

              Node 1 has 2 SCAN listeners and Node 2 has One.

              If the node 1 fails then SCAN listeners on that node will fail over to node 2 .

              Now node2 hosts all three SCAN listeners .When the NODE 1 comes back the 2 SCAN listeners will fail back to node 1 .


              Please correct me if I am wrong.
              Your understanding is correct.....
              In case of 2-node rac system, having two scna listener running in one node is expected behavior and acceptable in normal circumstances. (because oracle recommends to use 3 SCAN ips even if its 2 node rac).
              And yes when node 1 fails then the resources of SCAN VIP and SCAN Listener will failover to remaining node i.e node 2. And when node 2 is restored again, then again one set of SCAN VIP and SCAN Listener will relocate to it.

              Please see following lines from > http://www.oracle.com/technetwork/database/clustering/overview/scan-129069.pdf
              "In case, a 2-node-cluster is used (for which 3 IPs are still recommended for simplification reasons), one server in the
              cluster will host two sets of SCAN resources under normal operations. If the node where a SCAN VIP is running fails,
              the SCAN VIP and its associated listener will failover to another node in the cluster. If by means of such a failure the
              number of available servers in the cluster becomes less than three, one server would again host two sets of SCAN
              resources. If a node becomes available in the cluster again, the formerly mentioned dispersion will take effect and
              relocate one set accordingly."

              Edited by: 909592 on Apr 9, 2012 1:18 PM
              • 4. Re: If all SCAN listeners fails
                Vijay.Cherukuri-Oracle
                Thanks for your prompt reply

                --
                Thanks
                Vijay