Drop PDB commands in Oracle.

Check the status of PDBs present in Oracle Database:

SQL> show pdbs;
   CON_ID CON_NAME                   OPEN MODE  RESTRICTED
--------- -------------------------- ---------- ----------
        3 PDB3                       READ WRITE NO
        4 PDB4                       READ WRITE NO
OR 

SQL>  select con_id, name,open_mode from v$containers;

For dropped the database, we must shut down or close the PDB database:

SQL> alter pluggable database pdb4 close;

Pluggable database altered.

For drop the PDB database has two options:

Drop with including Datafiles:

SQL> drop pluggable database pdb4 including datafiles;
Pluggable database dropped.

Drop with keep datafiles:

SQL> drop pluggable database pdb4 keep datafiles;
Pluggable database dropped.