[Oracle DataBase Server 12.2 Installation on Oracle Linux 7.4]: Enable ARCHIVELOG Mode

When operating in ARCHIVELOG mode, after redo-log switching, a copy of the log is archived and saved to disk. This allows you to roll back the database to a specific point in the past (e.g., to a specific time) if necessary. When operating in ARCHIVELOG mode, you can create database backups without stopping the database (hot backup). This mode requires allocating additional server resources, i.e., taking resources away from other processes. By default, this option is disabled.

$ sqlplus / as sysdba

Check the database operating mode:

SQL> select log_mode from v$database;

LOG_MODE
------------
NOARCHIVELOG

Enable archivelog (if disabled)

SQL> shutdown immediate;
SQL> startup mount exclusive;
SQL> alter database archivelog;
SQL> alter database open;

SQL> select log_mode from v$database;

LOG_MODE
------------------------------------
ARCHIVELOG

Get additional information with the following command:

SQL> ARCHIVE LOG LIST

Database log mode              Archive Mode
Automatic archival             Enabled
Archive destination            USE_DB_RECOVERY_FILE_DEST
Oldest online log sequence     30
Next log sequence to archive   32
Current log sequence           32

SQL> quit