Oracle 12c Pluggable Database features

Oracle 12c Pluggable Database features 

* Each PDB has its own private data dictionary for customer-created database objects; CDB on the other hand as a whole has the data dictionary for the Oracle-supplied system each data dictionary defines its own namespace. In other words, there is global Data dictionary (CDB level) and local one (PDB level).
* There is a new split data dictionary architecture that allows a PDB to be quickly unplugged from one CDB and plugged into a different CDB
* Each PDB sees a read-only definition of the Oracle-supplied system
* There are global database initialisation parameters on CDB level and local ones. PDB parameters belong only to you particular PDB and will be persistent even after you unplug you PDB.
* Database users can be global (CDB) or local (PDB only). SYS and SYSTEM users exist in both DBs right at the beginning. If you create a new user in CDB you will see it in PDB also. In case of creation of a user on PDB level it will stay local.
* Temporary tablespaces can be global or local
* Redo logs and Undo tablspace are only global (on CDB level)
* Data Guard acts on the CDB as a whole; RMAN scheduled backups are done for the CDB as a whole; you can back up a selected PDB whenever you want to; you can do point-in-time
* An application connects, with no code changes, to a PDB; the system administrator connects to the CDB; the service named in the connect string specifies the destination PDB
* A PDB allows a clear declarative definition of an application; one PDB knows nothing of the other PDBs within the same CDB; each PDB is a hermetically sealed container. That ensures new level of DB independence and robust security