user creation on oracle 12c database

we have two kind of users available on oracle 12c database

1)local users       --> only for specific PDBS
2)common users --> users on CDB with hass to all PDBS

1)local users creation steps

SQL> alter session set container=pdb1;

Session altered.

SQL> create user user1_pdb1 identified by XXXXX;

User created.

SQL> grant pdb_dba to user1_pdb1;(its a special role for PDB)

Grant succeeded.

SQL> conn user1_pdb1/XXXX@pdb1
connected.

2)common user always start with c###
SQL> conn / as sysdba
SQL> create user c##bala identified by XXXXX;

User created.

SQL> grant dba to  c##bala;

Grant succeeded.

SQL> conn c##bala/XXXX;
Connected.
SQL> create table test_11dec2016_dba_obj as select * from dba_objects;


Table created.