Oracle 12c introduced the Mulitenant database concept where a container database is built and then subsequent databases can be plugged into the container.
  *  [[https://oracle-base.com/articles/12c/multitenant-overview-container-database-cdb-12cr1|Multitenant : Overview of Container Databases (CDB) and Pluggable Databases (PDB)]]
  *  [[https://oracle-base.com/articles/12c/multitenant-migrate-non-cdb-to-pdb-12cr1|Multitenant : Migrate a Non-Container Database (CDB) to a Pluggable Database (PDB) in Oracle Database 12c]]