Falshback from Common User Drop

$ export NLS_DATE_FORMAT='DD-MM-YYYY HH:MI:SS'
$ sqlplus / as sysdba
SQL> select flashback_on from v$DATABASE;

FLASHBACK_ON
------------------------
NO

SQL> shutdown immediate;
SQL> startup mount;
SQL> ALTER SYSTEM SET DB_FLASHBACK_RETENTION_TARGET=2880 SCOPE=BOTH;
SQL> ALTER DATABASE FLASHBACK ON;
SQL> ALTER DATABASE OPEN;

2)
SQL> ALTER PLUGGABLE DATABASE ALL OPEN;
SQL> ALTER PLUGGABLE DATABASE ALL SAVE STATE;

3) DROP USER
SQL> col username for a20
SQL> select USERNAME, COMMON, CON_ID from cdb_users
where username='C##_USER';

 USERNAME         COM     CON_ID
-------------------- --- ----------
C##_USER         YES      1
C##_USER         YES      6
C##_USER         YES      5
C##_USER         YES      4
C##_USER         YES      3

Log the SCN before dropping
SQL> select timestamp_to_scn(current_timestamp) from v$database;

TIMESTAMP_TO_SCN(CURRENT_TIMESTAMP)
-----------------------------------
                2812476


 SQL> drop user C##_USER cascade;
SQL> alter system switch logfile;
SQL> alter system switch logfile;
SQL> alter system switch logfile;
SQL> alter system switch logfile;
SQL> SHUTDOWN IMMEDIATE
SQL> STARTUP MOUNT
SQL> FLASHBACK DATABASE TO SCN 2812476;
SQL > ALTER DATABASE OPEN READ ONLY;
SQL> 
SQL> col username for a20
SQL> select USERNAME, COMMON, CON_ID from cdb_users
  2  where username='C##_USER';

USERNAME         COM     CON_ID
-------------------- --- ----------
C##_USER         YES      1

 SQL> ALTER PLUGGABLE DATABASE ALL OPEN READ ONLY;

SQL> select USERNAME, COMMON, CON_ID from cdb_users
where username='C##_USER';

USERNAME         COM     CON_ID
-------------------- --- ----------
C##_USER         YES      3
C##_USER         YES      5
C##_USER         YES      1
C##_USER         YES      4
C##_USER         YES      6


 SQL> SHUTDOWN IMMEDIATE
SQL>STARTUP MOUNT;
SQL> FLASHBACK DATABASE TO SCN 2812476;
Flashback complete.
SQL > ALTER DATABASE OPEN RESETLOGS;

3) Check user
SQL> conn C##_USER
Enter password:
Connected.
SQL> conn c##_USER@PDB2
Enter password:
Connected.
SQL> connect C##_USER@PDB2_2
Enter password:
Connected.


4) Backup  DB
$ rman target /
RMAN> BACKUP DATABASE PLUS ARCHIVELOG delete all input;
...
RMAN> exit;