How to check archive log generation per hour in Oracle

Run against the database instance. It sets an nls_date_format for the session.

set pages 1000
alter session set nls_date_format = 'DD-MON-YYYY HH24:MI:SS';
select trunc(COMPLETION_TIME,'HH') Hour,thread#,round(sum(BLOCKS*BLOCK_SIZE)/1024/1024/1024) GB,count(*) Archives from v$archived_log group by trunc(COMPLETION_TIME,'HH'),thread# order by 1;