we have used schedule job every 10 seconds for sendmail.
So we had many logs
whem i queried
select count(*) from dba_schedule_job_run_detail;
263201 rows selected.
So I used DBMS_SCHEDULER.PURGE_LOG package for purge log
keep 10 days of MAIL_ALERT_TIME job
SQL> exec dBMS_SCHEDULER.PURGE_LOG(log_history => 10, job_name => 'MAIL_ALERT_TIME');
or purge all every jobs