General characteristics of the 12c version :
- In previous versions the 12c version , all databases are not of type container .
- Starting with version 12c a database can be of container type or may remain conventional , non- CBD.
- The Oracle database on 12c version supports the new ” multitenant ” that allows several sub databases into a master database . The master database is a sub CBD and databases are kind of PDB .
- A container called ” ROOT” (CBD $ ROOT ) contains the ” tablespaces ” SYSTEM , SYSAUX , UNDO and TEMP and of course the control files and files ” redo log” .
- A container called ” SEED ” (PDB $ SEED) contains the SYSTEM, SYSAUX , TEMP , EXAMPLE used as a template to create new tablespaces PDB .
- All CDB always maintains a SEED and ROOT .
- SEED can not be opened for reads and writes but only for reading.