Data Guard #JoelKallmanDay
Apart from Exadata (been working the last 7 years with it) one of my favourite Oracle products is Data Guard.
I don't think I need to explain Data Guard
I have been using Data Guard since quite a while, it literally saved customers' business quite a few times.
It works way better than storage replication, something that gave already quite a bit of issues in the past at some of my customers, for the same reason as why you use RMAN to backup your Oracle Database ; Oracle knows exactly how an Oracle block / redo / transaction looks like and only copies over data to recover that transaction. Storage replications copies over every change also corruptions.
Before you just a had a physical standby and you had to type all the commands yourself to do a failover / switchover, but then came the Data Guard Broker, one command to type the broker does the rest.
Since 12.1 I don't see a reason not to use the Broker, works really as a charm.
Oracle extended the feature set a lot over the years :
- we can have a Snapshot Standby : a standby temporarily opened in read write and then flashbacked again to physical standby
- Active Data Guard : a standby opened in read only and actually applying redo
- DML Redirection : on Active Data Guard you can do DML of course this should be limited and it is not the goal to run OLTP load on the ADG
- An observer can be set up to provide automatic failover, called Fast Start Fail Over ( FSFO)
- reinstate a standby after a failover