Query Tuning:PPI not being used in select - response (3) by dnoeth

Partition elimination tries to eliminate partitions which are not used at all from a scan, but for each "tab.cola" there might be another pair of dates in tab2. Thus the best thing you might get is "enhanced by dynamic partition elimination".
 
You could also try to add
and tab1.date1 between (select min(date1) from tab2) and (select max(date2) from tab2)
and see if this helps.
Dieter