Before starting Redo Apply services, the physical standby database must be in the
MOUNT status. From 11g onwards, the standby database can also be in the
OPEN mode. If the redo transport service is in the
ARCH mode, the redo will be applied from the archived redo logfiles after being transferred to the standby database. If the redo transport service is in
LGWR, the Log network server (LNS) will be reading the redo buffer in SGA and will send redo to Oracle Net Services for transmission to the standby redo logfiles of the standby database using the RFS process. On the standby database, redo will be applied from the standby redo logs.
Redo apply can be specified either as a foreground session ...