This illustration shows a multi-instance primary database archiving online redo logs to a multi-instance standby database in a Real Application Clusters environment. In this configuration, there are two primary database instances: Primary Instance A and Primary Instance B. There are also two standby instances: Standby Receiving Instance C and Standby Recovery Instance D. The definition and purpose of receiving instances and recovery instances is described in the text following this illustration. Each of the primary instances uses a LGWR process to write to online redo logs and archived redo logs that are local to the primary instance. In addition, the LGWR process on Primary Instance A sends its changes over an Oracle Net network to the RFS process on Primary Instance B and to the RFS process on Standby Receiving Instance C. Primary Instance B sends its changes over an Oracle Net network to the RFS process on Standby Recovery Instance D. The RFS process on each standby instance writes to the local standby redo logs. This figure also shows how the ARCn process on Standby Receiving Instance C sends its changes over an Oracle Net network to the RFS process on Standby Recovery Instance D. The ARCn process on Standby Recovery Instance D also archives its changes to the local archived redo logs.