Archive logs are utilized by RMAN, Data Guard, Flashback and many others. If your going to enable archivelog mode on a real database thats important to you, I would recommend shutting down the database and doing a cold backup just in case. Keeping a 'final noarchivelog mode backup' seems to be a good and excepted practice. Enabling archive mode. Connect database as sys user to configure it in archivelog mode. oracle@12c $ sqlplus “/ as sysdba” // Archive log list: Database is in ‘No Archive Mode’. $ export ORACLESID= where is the name of the database $ sqlplus /nolog SQL connect / as sysdba; To enable ARCHIVELOG mode status, enter the following SQL commands: SQL Shutdown SQL Startup mount SQL Alter database archivelog; SQL alter database open; To check the ARCHIVELOG mode status, enter the following SQL command. CREATE NON-CDB ON ORACLE 12C IN SILENT MODE; Create Non-CDB on Oracle 12c using DBCA (GUI). Enable the database in Archivelog mode. It is recommended to take a full backup before/after you brought the database in archive log mode. Caution: Your use of any information or materials on this website is entirely at your own risk. In this topic, I will show how to change Archive Log Mode in Oracle Database. Enable Archive Log Mode in RAC: Archive Log Status: Stop database using srvctl: Start Database with mount mode in one node and change the mode: Startup using srvctl for RAC: Validation: Disable Archive Log Mode in RAC: Shutdown Database Using Continue reading.

Since the Redologs are created at container database level in 12c and not at pluggable database level. (Enabling archivelog at pluggable database level is not possible). Archiving is done at CDB's.
You can check archive log mode either by querying v$database or

Oracle Database Archivelog Mode

archivelog list
SQL> select name,open_mode,log_mode from v$database;
NAME OPEN_MODE LOG_MODE
--------- -------------------- ------------
ORCL READ WRITE NOARCHIVELOG
(OR)
SQL> archive log list
Database log mode Archive Mode
Automatic archival Disabled
Archive destination USE_DB_RECOVERY_FILE_DEST
Oldest online log sequence 11
Next log sequence to archive 13
Current log sequence 13
******************************
To enable the Archvielog mode
******************************
SQL> shutdown immediate;
Database closed.

Enable Archivelog Mode Oracle 12c Rac

Database dismounted.
ORACLE instance shut down.
SQL> startup mount;
ORACLE instance started.
Total System Global Area 788529152 bytes
Fixed Size 2929352 bytes
Variable Size 541068600 bytes
Database Buffers 239075328 bytes

Enable Archivelog Mode Oracle 12c Instance

Redo Buffers 5455872 bytes
Database mounted.
SQL> ALTER DATABASE ARCHIVELOG;
Database altered.
SQL> ALTER DATABASE OPEN;
Database altered.
SQL> select name,open_mode,log_mode from v$database;
NAME OPEN_MODE LOG_MODE
--------- -------------------- ------------
ORCL READ WRITE ARCHIVELOG
SQL> archive log list
Database log mode Archive Mode
Automatic archival Enabled

Archive Log Mode Oracle 12c

How To Enable Archivelog Mode Oracle 12c

Archive destination USE_DB_RECOVERY_FILE_DEST
Oldest online log sequence 11
Next log sequence to archive 13

Oracle Archivelog Mode

Current log sequence 13