Archivelog difference

Archivelog difference:
Following queries archivelog difference: Run this on primary database

SQL> ALTER SESSION SET NLS_DATE_FORMAT = 'DD-MON-YYYY HH24:MI:SS';


SQL> SELECT   a.thread#,  b. last_seq, a.applied_seq, a. last_app_timestamp, b.last_seq-a.applied_seq   ARC_DIFF FROM (SELECT  thread#, MAX(sequence#) applied_seq, MAX(next_time) last_app_timestamp FROM gv$archived_log WHERE applied = 'YES'  GROUP BY thread#) a, (SELECT  thread#, MAX (sequence#) last_seq FROM gv$archived_log GROUP BY thread#) b WHERE a.thread# = b.thread#;

   THREAD#   LAST_SEQ APPLIED_SEQ LAST_APP_TIMESTAMP     ARC_DIFF
---------- ---------- ----------- -------------------- ----------
         1         79          78 18-SEP-2014 04:14:01          1