Wednesday, April 6, 2011

Oracle Restart - a 11g New Feature

Oracle Restart is a new feature introduced to enhance the availability of Oracle database. I wasn't aware of this till recently. It basically allows various components of Oracle to restart automatically in a stand-alone (non-clustered) installation. This functionality is similar to what Clusterware does in a RAC setup. On Windows and Linux, we were able to achieve all this via creating a service or writing a script. But now it’s not required. So in a way, it also makes the age old practice of writing scripts to restart redundant.

Oracle instances and its dependent components restart automatically after any hardware or software failures and machine reboots. The components that can be restarted are –
  • Database instance
  • Oracle Listener
  • ASM instance
  • ONS (Oracle notification service)
It continuously monitors all the Oracle services started via it and restarts any of the failing services. It ensures that the components are starts in proper order e.g. starting the ASM instance before starting the database instance. What’s important is that Oracle restart is integrated with tools like SQL*Plus, LSNRCTL, and ASMCMD; so when you shut down the database or listener with the respective utilities, Oracle Restart does not interpret it as a failure and hence does not attempt to restart.

Much like clusterware, Oracle Restart also comes with a server control utility (SRVCTL); you should start/stop the components with SRVCTL.

In my opinion, this is a pretty useful tool and option to have. Gets rid of any additional scripting that would have required in day-to-day operations. Also serves as an introduction to how to manage services in a RAC which is a good thing for junior DBA's. The only problem the tool still looks for “ORA_CRS_HOME”, which is a bit weird given that it is supposedly for single (non-RAC) instance databases.

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