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-> Oracle RAC Clusterware Components

 

 Oracle RAC Clusterware Components

 

 

Oracle Clusterware includes the following processes:                                           Link to Oracle RAC clusterware startup sequence (11gR2)

 

1) Cluster Ready Services (CRS) 

          Functionality: RAC resource monitoring/ management   ==> all changes are written in the OCR

                                                  - start, stop of the resouces

                                                  - failover of the application resources

                                                  - node recovery

                                                  - automatically restarts t RAC resources when a failure occurs.

         

          RAC resources: a database, an instance, a service, a listener, a virtual IP (VIP) address, an application process

 

 

          Daemon process (on AIX, UNIX, Linux):  crsd

        

 

          Run as (on AIX, UNIX, Linux): root

 

          ps -ef | grep crsd
       
root 221524 1 0 May 26 - 3:33 /oracle/crs/10.2/bin/crsd.bin reboot
 

 

          Failure of the process: the crsd restarts automatically, without restarting the node.

 

 

  CRSd can run in 2 modes:

  

     reboot mode -> when crsd starts all the resources are restarted.

  

     restart mode -> when crsd starts the resources are started as these were before the shutdown.

 

 

   When CRS is installed on the cluster where a 3rd-party clusterware is integrated (there are 2 clusterware on the cluster)

 

                 -> CRSd manages:

                              -  Oracle RAC services and resources

 

 

   When CRS is the ONLY ONE clusterware on the cluster

 

                 -> CRSd manages:

                              -  Oracle RAC services and resources

                              -  the node membership functionality  (by CSSd, but CSS in managed by CRSd)

 

 

   COMMENT:

   In order to start the crsd we need:

                 - the public interface, the private interface and the virtual IP (VIP) should be up and running !

                 - these IPs must be pingable to each other.

 

 

 

2) Cluster Synchronization Services (CSS)

 

          Functionality: enables basic cluster services    ==> new/ lost node information is written to OCR

 

                                   - the node membership functionality

                                   - basic locking

 

          Daemon process (on AIX, UNIX, Linux):  ocssd

        

 

          Run as (on AIX, UNIX, Linux): oracle


        ps -ef | grep ocssd
       
oracle 229642 241940 1 May 26 - 3:36 /oracle/crs/10.2/bin/ocssd.bin
 

          Failure of the process: Node restart.

 

 

 

3) Event Management (EVM)

 

          Functionality: - a background process that publishes events that crs creates.

 

          Daemon process (on AIX, UNIX, Linux):  evmd

        

          Run as (on AIX, UNIX, Linux): oracle


        ps -ef | grep evmd
       
oracle 229633 241356 1 May 26 - 3:36 /oracle/crs/10.2/bin/evmd.bin
 

          Failure of the process: the evmd restarts automatically, without restarting the node.

 

 

 

4) Oracle Notification Service (ONS)

 

          Functionality: - a publish and subscribe service for communicating Fast Application Notification (FAN) events to clients.

 

          Daemon process (on AIX, UNIX, Linux):  ons

        

          Run as (on AIX, UNIX, Linux): oracle


        ps -ef | grep ons
       
oracle 233968 1 0 May 28 - 0:00 /oracle/crs/10.2/opmn/bin/ons -d
 

          Failure of the process:  -

 

 

 

5) RACG

 

          Functionality: - Runs server callout scripts when FAN events occur.

 

          Daemon process (on AIX, Linux):  racgimon (AIX), racgmain (Linux)

        

          Run as (on AIX, UNIX, Linux): oracle


        ps -ef | grep racgimon
       
oracle 385292 1 0 11:40:08 - 0:03 /oracle/db/10.2/bin/racgimon startd MYDB

         

         Failure of the process:  -

 

 

 

6) Process Monitor Daemon (OPROCD)    (cssdagent from 11gR2)

 

          Functionality: - is the I/O fencing solution which monitors the Cluster Node (I/O fencing )

                                   - when the Nx node fails, no other node can modify the Nx node resources

 

          Daemon process (on AIX, Linux):  racgimon (AIX), racgmain (Linux)

        

          Run as (on AIX, UNIX, Linux): root


        ps -ef | grep oprocd
       
root 184346 201058 0 May 27 - 0:06 /oracle/crs/10.2/bin/oprocd run -t 1000 -m 400
 

          COMMENT: In this case oprocd wakes up every minute to get the current time. If it is within 400ms range with the last result it will go back to sleep again otherwise it will reboot the node.         

 

         Failure of the process:  Node restart (=node reboot).

 

 

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