For all offerings using Oracle Database 19c or later, if you are not licensed for Oracle Multitenant, then you may have up to 3 user-created PDBs in a given container database at any time. For all offerings using Oracle Database 12.1 through 18c, if you are not licensed for Oracle Multitenant, then the container database architecture is available in single-tenant mode, that is, with one user-created PDB, one user-created application root, and one user-created proxy PDB.
EE: Extra cost option; if you are licensed for Oracle Multitenant, then you can create up to 252 PDBs.
ODA and Exa: Extra cost option; if you are licensed for Oracle Multitenant, then you can create up to 4096 PDBs.
ExaCS/CC, DBCS EE-HP, and DBCS EE-EP: Included option; you can create up to 4096 PDBs.