QSYS2.IFS_OBJECT_STATISTICS: ACCESS_TIMESTAMP vs LAST_USED_TIMESTAMP

Trying to determine usage of IFS stream files.

Using QSYS2.IFS_OBJECT_STATISTICS SQL table, I'm seeing LAST_USED_TIMESTAMP values lower than ACCESS_TIMESTAMP values, by anything up to 12 hours. I can't find any documentation on the field contents.

The Qp0lGetAttr()--Get Attributes API says:

"Last used date. The number of seconds since the Epoch that corresponds to the date the object was last used." (Not sure what kind of a value this is.)

"ACCESS_TIMESTAMP. The time that the object's data was last accessed."

If I open a file with EDTF the ACCESS_TIMESTAMP changes, but the LAST_USED_TIMESTAMP doesn't. I would expect them to be the same.

Can anyone offer enlightenment? I'm leaning towards using ACCESS_TIMESTAMP.

Here is some (ugly) SQL that show the difference if anyone wants to experiment.

WITH ifs AS
(
SELECT PATH_NAME name
,OBJECT_TYPE AS Type
,dec(days_used_count, 3, 0) AS Days
,create_timestamp Created
,access_timestamp Accessed
,data_change_timestamp Changed
,last_used_timestamp Used
,DATA_SIZE Size
,OBJECT_OWNER Owner

FROM TABLE (
QSYS2.IFS_OBJECT_STATISTICS(
START_PATH_NAME => '/home/lennons/github',
SUBTREE_DIRECTORIES => 'YES',
object_type_list => '*ALLSTMF')
) AS t
),
ifs2 as (
select timestampdiff(4,char(accessed - used)) as Mins_Diff
,a.* from ifs as a
)
-- Accessed seems to date I open the file, e.g. with EDTF.
-- Not sure what Used is.
SELECT Name
,Days
,Accessed
,Used
,mins_diff
,mins_diff/60 as hours
,mod(mins_diff,60) as mins
FROM IFS2
ORDER BY Accessed DESC;