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Thread: Oracle Clusterware processes and Components

  1. #1
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    Oracle Clusterware processes and Components

    Oracle Clusterware processes for 10g

    Cluster Synchronization Services (ocssd) — Manages cluster node membership and runs as the oracle user; failure of this process results in cluster restart.

    Cluster Ready Services (crsd) — The crs process manages cluster resources (which could be a database, an instance, a service, a Listener, a virtual IP (VIP) address, an application process, and so on) based on the resource's configuration information that is stored in the OCR. This includes start, stop, monitor and failover operations. This process runs as the root user

    Event manager daemon (evmd) —A background process that publishes events that crs creates.

    Process Monitor Daemon (OPROCD) —This process monitor the cluster and provide I/O fencing. OPROCD performs its check, stops running, and if the wake up is beyond the expected time, then OPROCD resets the processor and reboots the node. An OPROCD failure results in Oracle Clusterware restarting the node. OPROCD uses the hangcheck timer on Linux platforms.

    RACG (racgmain, racgimon) —Extends clusterware to support Oracle-specific requirements and complex resources. Runs server callout scripts when FAN events occur.


    Oracle Clusterware Components

    Voting Disk — Oracle RAC uses the voting disk to manage cluster membership by way of a health check and arbitrates cluster ownership among the instances in case of network failures. The voting disk must reside on shared disk.

    Oracle Cluster Registry (OCR) — Maintains cluster configuration information as well as configuration information about any cluster database within the cluster. The OCR must reside on shared disk that is accessible by all of the nodes in your cluster

  2. #2
    Oracle Clusterware processes and Components:

    1) Cluster Ready Services (CRS):-

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

    - start, stop of the resouces

    - automatically restarts the RAC resources when a failure occurs.

    - node recovery

    - failover of the application resources

    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 21 Feb 12 5:24 /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 the ONLY ONE clusterware on the cluster

    -> CRSd manages:
    - Oracle RAC services and resources (apart from node membership)


    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/ deleted(lost) node information is written to OCR.

    -node membership functionality
    -lock management
    -group management

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

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

    ps -ef | grep ocssd
    oracle 229642 241940 21 Feb-12 - 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,i,e Callouts generate.

    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.


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

    4) OPROCd:--

    Functionality: - is the I/O fencing solution which monitors the Cluster Node (I/O fencing ) and
    to prevent the corruption.

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

    ps -ef | grep oprocd
    root 184346 201058 1 Feb 12 - 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).


    Cluster ware Components:--

    There are two components:--

    1)Voting Disk and

    2)Oracle Cluster Registry(OCR)

    1) Voting Disk:-- Oracle Clusterware uses the voting disk to determine which instances are members of a cluster. The voting disk must reside on a shared disk.
    For high availability, Oracle recommends that we have a minimum of three voting disks.
    We can have up to 32 voting disks in our cluster.

    2) Oracle Cluster Registry(OCR):-- Oracle Clusterware uses the OCR to store and manage information about the components that Oracle Clusterware controls, such as Oracle RAC databases, listeners, VIPs, and services and any applications.

    --->The OCR must reside on a shared disk that is accessible by all of the nodes in the cluster.

    ---->Oracle Clusterware can multiplex the OCR.

    ---->We can replace a failed OCR online.

    ---->Oracle Clusterware requires that each node be connected to a private network by way of a private interconnect.

    ---->For redundancy, we can have up to 32 voting disks and a mirror of the OCR.
    Last edited by vineettyagi; 02-22-2012 at 10:40 AM.

  3. #3
    Expert Oracle Administrator
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    Good post Tyagi

  4. #4
    Oracle DBA
    Join Date
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    Please Verify it

    Quote Originally Posted by vineettyagi View Post
    Oracle Clusterware processes and Components:

    1) Cluster Ready Services (CRS):-

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

    - start, stop of the resouces

    - automatically restarts the RAC resources when a failure occurs.

    - node recovery

    - failover of the application resources

    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 21 Feb 12 5:24 /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 the ONLY ONE clusterware on the cluster

    -> CRSd manages:
    - Oracle RAC services and resources (apart from node membership)


    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/ deleted(lost) node information is written to OCR.

    -node membership functionality
    -lock management
    -group management

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

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

    ps -ef | grep ocssd
    oracle 229642 241940 21 Feb-12 - 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,i,e Callouts generate.

    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.


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

    4) OPROCd:--

    Functionality: - is the I/O fencing solution which monitors the Cluster Node (I/O fencing ) and
    to prevent the corruption.

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

    ps -ef | grep oprocd
    root 184346 201058 1 Feb 12 - 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).


    Cluster ware Components:--

    There are two components:--

    1)Voting Disk and

    2)Oracle Cluster Registry(OCR)

    1) Voting Disk:-- Oracle Clusterware uses the voting disk to determine which instances are members of a cluster. The voting disk must reside on a shared disk.
    For high availability, Oracle recommends that we have a minimum of three voting disks.
    We can have up to 32 voting disks in our cluster.

    2) Oracle Cluster Registry(OCR):-- Oracle Clusterware uses the OCR to store and manage information about the components that Oracle Clusterware controls, such as Oracle RAC databases, listeners, VIPs, and services and any applications.

    --->The OCR must reside on a shared disk that is accessible by all of the nodes in the cluster.

    ---->Oracle Clusterware can multiplex the OCR.

    ---->We can replace a failed OCR online.

    ---->Oracle Clusterware requires that each node be connected to a private network by way of a private interconnect.

    ---->For redundancy, we can have up to 32 voting disks and a mirror of the OCR.

    Please check the below Authenticity of below line.

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



    Any Failure or death of the CRSd can cause node failure, so it automatically reboots the nodes to avoid data corruption.

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