11 Replies Latest reply: Aug 4, 2010 5:41 AM by 677285 RSS

    Master Node on RAC

    585179
      Hi,


      Just would like to know, how to know which node is the master on RAC, is there any command for this?


      cheers

      fzheng
        • 1. Re: Master Node on RAC
          578825
          There is no concept of master node in RAC. In what context are you looking for a master node ?
          • 2. Re: Master Node on RAC
            516450
            One way to find that information is to look at the log file $ORA_CRS_HOME/log/`hostname`/cssd/ocssd.* files, you would find something like this:

            ocssd.l05:[    CSSD]CLSS-3001: local node number 1, master node number 1
            ocssd.l05:[    CSSD]2007-02-08 13:58:44.508 [507920] >TRACE: clssgmEstablishMasterNode: MASTER for 21 is node(1) birth(6)
            ocssd.l05:[    CSSD]2007-02-08 13:58:44.508 [507920] >TRACE: clssgmMasterCMSync: Synchronizing group/lock status
            ocssd.l05:[    CSSD]2007-02-08 13:58:44.514 [507920] >TRACE: clssgmMasterSendDBDone: group/lock status synchronization complete
            ocssd.l05:[    CSSD]CLSS-3001: local node number 1, master node number 1
            ocssd.l05:[    CSSD]2007-02-08 14:01:46.236 [524304] >TRACE: clssgmEstablishMasterNode: MASTER for 22 is node(1) birth(6)
            ocssd.l05:[    CSSD]2007-02-08 14:01:46.236 [524304] >TRACE: clssgmMasterCMSync: Synchronizing group/lock status
            ocssd.l05:[    CSSD]2007-02-08 14:01:46.241 [524304] >TRACE: clssgmMasterSendDBDone: group/lock status synchronization complete

            But, this information is not really not that critical for ongoing operations or regular maintenance.....and just informational for all practical purposes.

            HTH
            Thanks
            Chandra Pabba
            • 3. Re: Master Node on RAC
              413311
              can someone explain the concepts behind the 'master' node in RAC ?
              • 4. Re: Master Node on RAC
                561093
                Hi,

                During system boot, the node which attains the ACTIVE state is authorized to be a master node by Cluster Synchronization Service.

                Other nodes in the member will request the master node for blocks in CR/CU mode. If the block is available with any other member of the cluster, the Master node orders that node to ship the block to the requesting node. If the block doesn't exist then the requesting is instructed by the Master node to fetch the block from the disk.

                Regards
                • 5. Re: Master Node on RAC
                  516450
                  Citrus,

                  Just a small note....since when I read your response it looks like you are referring to Master at the cluster level to be the same as the Resource Master and that it is in the same context...
                  During system boot, the node which attains the ACTIVE
                  state is authorized to be a master node by Cluster
                  Synchronization Service.
                  ---This is different from what you are referring to below. This is a merely a Master at the cluster level.
                  Other nodes in the member will request the master
                  node for blocks in CR/CU mode. If the block is
                  available with any other member of the cluster, the
                  Master node orders that node to ship the block to the
                  requesting node. If the block doesn't exist then the
                  requesting is instructed by the Master node to fetch
                  the block from the disk.
                  ----This is called the Resource Master, which is different than the master designated at the cluster level. A Resource Master exists for each block and any node can be master for block. When it comes to being a resource master all nodes are treated equal....meaning a node needn't be a Master at the cluster level to be a resource master.

                  Thanks
                  Chandra
                  • 6. Re: Master Node on RAC
                    601894
                    ora.pcard.db ONLINE ONLINE on rspwd03
                    ora.pcard.hps.cs ONLINE ONLINE on rspwd01
                    ora.pcard.hps.pcard1.srv ONLINE ONLINE on rspwd01
                    ora.pcard.hps.pcard2.srv ONLINE ONLINE on rspwd02
                    ora.pcard.pcard1.inst ONLINE ONLINE on rspwd01
                    ora.pcard.pcard2.inst ONLINE ONLINE on rspwd02
                    ora.pcard.pcard3.inst ONLINE ONLINE on rspwd03
                    ora.pcard.pcard4.inst ONLINE ONLINE on rspwd04

                    I have four instance pcard1,2,3,4 etc..
                    and I created Oracle service " hps" running on node 1 and node2.

                    But what is ora.pcard.db ..it is running on node 3 only
                    ora.pcard.hps.cs this is running on node 1 only.
                    Bharat
                    • 7. Re: Master Node on RAC
                      516450
                      Hi Bharat,

                      >>>>>But what is ora.pcard.db ..it is running on node 3 only

                      Remember....in RAC, we would have multiple instances for a single database...therefore you would seen only one *.db running on any one of the nodes.

                      >>>>>ora.pcard.hps.cs this is running on node 1 only.

                      May be this particular service is created to run on only one instance/node.

                      HTH

                      Thanks
                      Chandra Pabba
                      • 8. Re: Master Node on RAC
                        MarkusM-Oracle
                        Chandra is correct.

                        Therefore, I would just like to add that the mastering on Clusterware level is usually transparent to the user (as you indicated). There are some dependencies internally on the master node, but apart from that, the master on Clusterware level should not be taken into account by the user. Especially, there is no need to consider failure scenarios around the master placement, as it was suggested in some other places before. The master concept is totally redundant. If a master node fails, another one will become the master in course of the cluster re-configuration process.

                        Regarding the resource mastering in the RAC layer, the master node is the node that grants locks on blocks basically (simplified). Those two master concepts are, as Chandra pointed out, completely independent.
                        • 9. Re: Master Node on RAC
                          588514
                          Hi all, I noticed that only the master node does the automatic backup of ocr, and it saves them in
                          ${ORA_CRS_HOME}/cdata/${CLUSTER_NAME} , so it would be nice to have a simple way to aumatically get teh master node name to copy such backups on other devices, for example.

                          However i didn't fnid any simple way to get this.

                          Any ideas ?

                          andrea
                          • 10. Re: Master Node on RAC
                            New DBA
                            in the V$GES_RESOURCE has the Master column.
                            It contains the Node No.The Particular Node acts as the Master node
                            • 11. Re: Master Node on RAC
                              677285
                              There are two things in RAC , one is Master Node for the entire cluster and the other is Master Node for a specific block. Both r different. The one mentioned in the log files is the master node of the cluster. Any node can become the master node of a particulat block.

                              http://orainternals.wordpress.com/2010/03/25/rac-object-remastering-dynamic-remastering/

                              This link will explain more about the second part.