Since the Redologs are created at container database level in 12c and forwards. Its notcreated at pluggable database level.

Its not possible to Enabling archivelog at pluggable database level. You need to do it on CDB level.

Let us see how we can enable archive log.

1. Check archive log mode by below query,

SQL> select name,open_mode,log_mode from v$database;

NAME OPEN_MODE LOG_MODE

CDB READ WRITE NOARCHIVELOG

(OR)

2. Enable the Archive-log mode

— Stop DB first

SQL> shutdown immediate;
Database closed.
Database dismounted.
ORACLE instance shut down.

— Start DB in mount state
SQL> startup mount;
ORACLE instance started.

— Enable ARCHIVELOG

SQL> ALTER DATABASE ARCHIVELOG;
Database altered.

— Open database
SQL> ALTER DATABASE OPEN;

Database altered.

3. Check current status of archive by using below query

SQL> select name,open_mode,log_mode from v$database;

NAME OPEN_MODE LOG_MODE

CDB READ WRITE ARCHIVELOG