In a Oracle 12c multitenant DB instance with multiple PDBs, is it possible to enable
ARCHIVELOG mode on a single PDB?
Because all PDBs share the same redo log files, it's not possible to enable archive log mode only for a specific PDB. All PDBs share the archive log mode of the CDB.
Remember, the PDBs themselves don't have any instance (processes and memory areas) or control file and redo logs