Common Users & SYSDBA with #Oracle 12c:
SQL> select name,open_mode,con_id from v$pdbs;
NAME OPEN_MODE CON_ID
------------------------------ ---------- ----------
PDB$SEED READ ONLY 2
PDBORCL READ WRITE 3
APEXPDB READ WRITE 4
SQL> select * from v$pwfile_users;
USERNAME SYSDB SYSOP SYSAS SYSBA SYSDG SYSKM CON_ID
------------------------------ ----- ----- ----- ----- ----- ----- ----------
SYS TRUE TRUE FALSE FALSE FALSE FALSE 0
SQL> create user c##_sys identified by oracle container=all;
User created.
SQL> grant sysdba to c##_sys container=all;
Grant succeeded.
SQL> select * from v$pwfile_users;
USERNAME SYSDB SYSOP SYSAS SYSBA SYSDG SYSKM CON_ID
------------------------------ ----- ----- ----- ----- ----- ----- ----------
SYS TRUE TRUE FALSE FALSE FALSE FALSE 0
C##_SYS TRUE FALSE FALSE FALSE FALSE FALSE 0
C##_SYS can now do anything to any PDB
