The services required on the primary database are:

• Log WRITER Process (LGWR) – Collects redo information and updates the online redo logs. It can ALSO create local archived redo logs and transmit online redo to standby databases.
• Archiver Process (ARCn) – One or more archiver processes make copies of online redo logs either locally or remotely for standby databases.
• Fetch Archive Log (FAL) Server – Services requests for archive redo logs from FAL clients running on multiple standby databases. Multiple FAL servers can be run on a primary database, one for each FAL REQUEST. .
• The services required on the standby database are:
• Fetch Archive Log (FAL) Client – Pulls archived redo log files from the primary site. Initiates transfer of archived redo logs when it detects a gap sequence.
• Remote FILE Server (RFS) – Receives archived and/or standby redo logs from the primary database.
• Archiver (ARCn) Processes – Archives the standby redo logs applied by the managed recovery process (MRP).
• Managed Recovery Process (MRP) – APPLIES archive redo log information to the standby database

The services required on the primary database are: