To verify whether TIMED_STATISTICS changed between the snapshots used in your AWR Diff report, you can check the historical parameter values stored in AWR.
Method 1: Check Parameter History from AWR
SELECT s.snap_id,
s.instance_number,
TO_CHAR(s.begin_interval_time,'DD-MON-YYYY HH24:MI') begin_time,
p.value
FROM dba_hist_parameter p,
dba_hist_snapshot s
WHERE p.snap_id = s.snap_id
AND p.dbid = s.dbid
AND p.instance_number = s.instance_number
AND p.parameter_name = 'timed_statistics'
ORDER BY s.snap_id;
Look for changes in the VALUE column (TRUE/FALSE).
Method 2: Check Only the Snapshots Used in the Report
If your report compared snapshots 100-101 with 200-201:
SELECT snap_id,
value
FROM dba_hist_parameter
WHERE parameter_name = 'timed_statistics'
AND snap_id IN (100,101,200,201)
ORDER BY snap_id;
Example output:
SNAP_ID VALUE
------- -----
100 FALSE
101 FALSE
200 TRUE
201 TRUE
This would explain the warning.
Method 3: Find Exactly When the Value Changed
SELECT snap_id,
value,
LAG(value) OVER (ORDER BY snap_id) prev_value
FROM dba_hist_parameter
WHERE parameter_name = 'timed_statistics'
ORDER BY snap_id;
Or show only the change point:
WITH p AS
(
SELECT snap_id,
value,
LAG(value) OVER (ORDER BY snap_id) prev_value
FROM dba_hist_parameter
WHERE parameter_name = 'timed_statistics'
)
SELECT *
FROM p
WHERE value <> prev_value;
Method 4: Check Database Restart Between Snapshots
Sometimes the warning appears because the database was restarted and initialization parameters changed.
SELECT snap_id,
startup_time,
begin_interval_time
FROM dba_hist_snapshot
ORDER BY snap_id;
Look for a change in STARTUP_TIME between your snapshot ranges.
RAC Environment
If this is RAC, check all instances:
SELECT snap_id,
instance_number,
value
FROM dba_hist_parameter
WHERE parameter_name = 'timed_statistics'
ORDER BY instance_number, snap_id;
A change on even one instance can trigger the warning.
