Data Guard uses two terms when cutting over the standby server, switch-over which is a planned and failover which a unplanned event .
1.) Notifies the primary database that a switchover is about to occur
2.) Disconnect all users from the primary database
3.) Generate a special redo record that signals the End of Redo (EOR)
4.) Converts the primary database into a standby database
- Maximum Performance - possible chance of data loss
- Maximum Availability - possible chance of data loss
- Maximum Protection - no data loss
- What is the current state of the primary database just before the transition? Is it available?
- What is the state of the selected standby database to be used in the role transition at the time of transition?
- Is the standby database configured as a physical or logical standby database?
Hence finally we come to conclusion that the order to setup Data Guard is the following :
- The primary database is up and running
- Create a standby database
- Setup the redo transport rules
- Create the SRL files
- Execute one of the following
SQL> alter database set standby to maximum performance; //(default)
SQL> alter database set standby to maximum availability;
SQL> alter database set standby to maximum protection;
Reference : http://www.datadisk.co.uk