Configuration:
How long do you want to keep metrics data? 30 Days 
How often do you want to run the truncate process on expired date? 1 Hour 

HOWEVER, upon doing a max and min on starttime and logintime on the metrics tables, the stanrttime seem to extend beyond 30 days.


Analysis:
Reviewed the Delete statement issue by the application. 

DELETE FROM   "VDL_METRICS"."metrics_resources_usage"
      WHERE       "nodehost" = 'stludvpcprd02.monsanto.com'
              AND "nodeport" = 9400
              AND "cluster" = 'PRD_Cluster'
              AND "starttime" <
                    TO_TIMESTAMP ('2018-02-13 19:10:15.904',
                                  'YYYY-MM-DD HH24:MI:SS.FF')

Some entries for Cluster was set to ‘NULL’ in customer environment. All those entries were ignored because of the above DELETE statement. Hence the Min(Starttime) extended beyond the 30 day mark.