In earlier releases prior to Oracle 18c, while we could enable Data Guard for a Multitenant Container/Pluggable database environment, we were restricted when it came to performing a Switchover or Failover – it had to be performed at the Container Database (CDB) level.
This meant that a database role reversal would affect each and every PDB hosted by the CDB undergoing a Data Guard Switchover or Failover.
In Oracle 12c Release 2, a new feature called refreshable clone PDB was introduced. A refreshable clone PDB is a read-only clone that can periodically synchronize itself with its source PDB.
This synchronization could be configured to happen manually or automatically based on a predefined interval for the refresh.
In Oracle 18c a new feature has been added using the refreshable clone mechanism which enables us to now perform a switchover at the individual PDB level. So we are enabling high availability at the PDB level within the CDB.
We can now issue a command in Oracle 18c like this:
SQL> alter pluggable database orclpdb1
refresh mode manual
After the switchover completes, the original source PDB becomes the refreshable clone PDB (which can only be opened in
READ ONLY mode), while the original refreshable clone PDB is now open in read/write mode functioning as a source PDB.