12c Multi-Tenant CDB database parameters keep updating

Hi All,

We have a 12.1.0.2.3 CDB with 2 PDBs on Solaris 10. 

We recently were experiencing a performance issue and at the request of support had changed system parameters such as: optimizer_features_enable and optimizer_secure_view_merging.

The performance issue was resolved with a re-write of the query but it seems that when I check table: dba_hist_parameter, those parameters we modified once before, seem to be changing back and forth over and over every hour according to the snapshot history.

The query to verify when the parameters keep changing is:

select c.name,c.value,hp.value,

max((select begin_interval_time from dba_hist_snapshot where snap_id=hp.snap_id))