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Note: The article ( named Oracle restart ) was taken from www.in-oracle.com.

Oracle Restart improves the availability of your Oracle database. When you install Oracle Restart, various Oracle components can be automatically restarted after a hardware or software failure or whenever your database host computer restarts. Oracle Restart runs periodic check operations to monitor the health of these components. If a check operation fails for a component, the component is shut down and restarted.

Oracle Restart is used in standalone server (non-clustered) environments only. For Oracle Real Application Clusters (Oracle RAC) environments, the functionality to automatically restart components is provided by Oracle Clusterware. Oracle High Availability Services (ohasd) play Oracle Restart role in 11gR2.

Oracle Components Automatically Restarted by Oracle Restart

  - Database instance  -> Oracle Restart can accommodate multiple databases on a single host computer.

  - Oracle Net listener

  - Database services  -> Does not include the default service created upon installation because it is automatically managed by Oracle Database, and does not include any default services created during database creation.

  - Oracle Automatic Storage Management (Oracle ASM) instance

  - Oracle ASM disk groups  -> Restarting a disk group means mounting it.

  - Oracle Notification Services (ONS/eONS)  -> In a standalone server environment, ONS/eONS can be used in Oracle Data Guard installations for automating failover of connections between primary and standby database through Fast Application Notification (FAN). ONS/eONS is a service for sending FAN events to integrated clients upon failover.

ATTENTION !!!
        

   When you start a component with SRVCTL, any components on which this component depends are automatically started first, and in the proper order.
   When you start a component with SQL*Plus (or another utility), other components in the dependency chain are not automatically started; you must ensure that any components on which this component depends are started.

   When Oracle Restart is installed, many operations (but not all !!! ) that create Oracle components automatically add the components to the Oracle Restart configuration.

Note: The article ( named Oracle restart ) was taken from www.in-oracle.com.