- Any recent change (init.ora parameter, new/droped/altered index, table
structure, partition or DATABASE UPGRADE or PATCH etc)?
- Run AWR report for that period and share it. If you do not have that licence
then trace that report and trca (trace analyzer) it.
- How old is statistic (any change in collecting them)?
After this we can discuss …Toad has nothing with changing execution plans and
this is your problem.