archive log gape with Standby

Primary:
SQL> select thread#, max(sequence#) "Last Primary Seq Generated"
from v$archived_log val, v$database vdb
where val.resetlogs_change# = vdb.resetlogs_change#
group by thread# order by 1;

PhyStdby:
SQL> select thread#, max(sequence#) "Last Standby Seq Received"
from v$archived_log val, v$database vdb
where val.resetlogs_change# = vdb.resetlogs_change#
group by thread# order by 1;

PhyStdby:
SQL>select thread#, max(sequence#) "Last Standby Seq Applied"
from v$archived_log val, v$database vdb
where val.resetlogs_change# = vdb.resetlogs_change#
and val.applied in ('YES','IN-MEMORY')
group by thread# order by 1;


PhyStdby:
SQL> select al.thrd "Thread", almax "Last Seq Received", lhmax "Last Seq Applied" , almax-lhmax "Sequence Difference"
from (select thread# thrd, max(sequence#) almax
from v$archived_log
where resetlogs_change#=(select resetlogs_change# from v$database)
group by thread#) al,
(select thread# thrd, max(sequence#) lhmax
from v$log_history
where resetlogs_change#=(select resetlogs_change# from v$database)
group by thread#) lh
where al.thrd = lh.thrd;​