ORA-19595: archivelog already included in backup conversation

If a standby database is brought down and then later
restarted then RMAN backups may fail with:
RMAN-00571: ===========================================================
RMAN-00569: =============== ERROR MESSAGE STACK FOLLOWS ===============
RMAN-00571: ===========================================================
RMAN-03009: failure of backup command on ORA_DISK_1 channel at 05/18/2004 10:00:56
ORA-19595: archivelog /ora_logs/archivelogs/2_6512.arc already included in backup conversation

Workaround:
Find the duplicate archivelog names using following query -
select al.recid, al.name from v$archived_log al
where al.status = 'A' and al.standby_dest= 'NO'
minus
select al.recid, al.name from v$archived_log al,
(select max(recid) recid
from v$archived_log
where status = 'A'
group by name) keepal
where al.status = 'A'
and al.standby_dest = 'NO'
and keepal.recid = al.recid;

Then:
RMAN> catalog archivelog '';

This will register the missing archivelogs.