2026-03-12 20:23:15

tpt/ash/sample_drift.sql

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+-- Copyright 2018 Tanel Poder. All rights reserved. More info at http://tanelpoder.com
+-- Licensed under the Apache License, Version 2.0. See LICENSE.txt for terms & conditions.
+
+-- check if there's sample time drift in ASH (should be every 1 seconds)
+-- it makes sense to run this only on active systems where every sample there
+-- are some active sessions seen
+
+select * from (
+    select 
+        to_char(sample_time,'YYYYMMDD HH24:MI:SS')
+      , sample_time-lag(sample_time) over(order by sample_time) delta
+    from 
+        (select distinct sample_time from v$active_session_history)
+)
+where
+    delta < numtodsinterval(2, 'second') -- eliminate ASH sample gaps without captured DB activity
+/
+
+