ARCHIVELOG Mode 

Use

After installation, the database runs in ARCHIVELOG mode. This configuration ensures that all written online redo log files are automatically archived after a redo log switch (using the background process ARCH). Only when the contents of the online redo log file have been saved successfully (as an offline redo log file in the archive directory), can the file be written to again.

Prerequisites

You must use ARCHIVELOG mode if you want to make backups online. If your database - for whatever reason - is in NOARCHIVELOG mode, you must restart the database and start ARCHIVELOG mode explicitly.

Activities

The database profiles provided with your R/3 System are configured to start the Oracle archiving process (ARCH) automatically.
See Archiving Parameters

You can configure ARCHIVELOG mode in the SAPDBA menu. To do this, select Archive mode ® Toggle database log mode. SAPDBA shuts down the database, configures the database mode, and restarts the database.
See SAPDBA: Archive Mode

You can also set ARCHIVELOG mode with the Oracle program SVRMGR:

SVRMGR> connect internal
SVRMGR> startup mount
SVRMGR> alter database archivelog;
SVRMGR> alter database open;
SVRMGR> archive log list

When archivelog appears in the database log mode display, this means you have correctly activated the ARCHIVELOG mode. Use the SAP utility program BRBACKUP to perform an offline backup of the database.

See Backing Up the Database with SAPDBA