In Oracle 10g RAC, when an instance goes down, services running on that instance are relocated to other available instances. But when that instance comes back up, those relocated services need to be manually put back to their preferred instance. By using FAN callouts, we can automate this task.

Using Oracle's heterogenous services also known as HS, we can make a connection to non-Oracle databases and access the data remotely. I used MS SQL server as the target non-Oracle database on Windows and used HS to access from Oracle database residing on Linux. Here, we'll see step by step instructions on how to set up a connection from Oracle database to Microsoft SQL server.

This time around, we'll do a switchover and switchback exercise using Oracle dataguard broker. If you need help on setting up the broker, refer my previous post How to setup DGMGRL, broker with example. We'll see how easy it is to switchover using just one command provided the broker is configured correctly. We'll also cover sample examples along with troubleshooting tips and comprehensive sanity checks.

Data Guard broker helps to efficiently manage a dataguard configuration through a client connection to any database in the configuration and it's very easy to switchover/failover with one command thereby minimizing overall downtime associated with planned/unplanned outage. It's also integrated with CRS so that database role changes occur smoothly and seamlessly. Here, we'll see how easy it is to setup using command line interface DGMGRL with an example.