The following query finds all enabled custom alerts. You can comment out the very last two lines (alr.enabled_flag and alr.created_by) to display all both enabled and disabled alerts.
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-- Query to find Custom Oracle Alert
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SELECT alr.application_id,
alr.alert_id,
alr.alert_name,
alr.start_date_active,
alr.description,
alr.sql_statement_text
FROM ALR.ALR_ALERTS alr
WHERE alr.created_by <> 1 --
show only custom alerts
AND
alr.enabled_flag = 'Y'; -- show only enabled alerts