Monitor standby background process 

SELECT DATABASE_ROLE, DB_UNIQUE_NAME INSTANCE, OPEN_MODE, PROTECTION_MODE, PROTECTION_LEVEL, SWITCHOVER_STATUS FROM V$DATABASE; 

View dataguard message or errors 

SELECT MESSAGE FROM V$DATAGUARD_STATUS; 

Last log applied/Received in standby 

select 'Last Log applied : ' Logs, to_char(next_time,'DD-MON-YY:HH24:MI:SS') Time

from v$archived_log

where sequence# = (select max(sequence#) from v$archived_log where applied='YES')

union

select 'Last Log received : ' Logs, to_char(next_time,'DD-MON-YY:HH24:MI:SS') Time

from v$archived_log

where sequence# = (select max(sequence#) from v$archived_log); 

Get standby redo log info 

set lines 100 pages 999

col member format a70

select st.group#

, st.sequence#

, ceil(st.bytes / 1048576) mb

, lf.member

from v$standby_log st

, v$logfile lf

where st.group# = lf.group#

/ 

Monitor recovery progress in standby db 

select to_char(START_TIME,'DD-MON-YYYY HH24:MI:SS') "Recovery Start Time",to_char(item)||' = '||to_char(sofar)||' '||to_char(units) "Progress"

from v$recovery_progress where start_time=(select max(start_time) from v$recovery_progress);