REM Huristics is not shifting from primary resource to secoundary resource-Pl suguest

Hi

There is requirement to shift from primary resource to secounday resource by using mode priority..

1)REM Huristics is not shifting from primary resource to secoundary resource by using mode priority when primary resource is overloaded-Please suguest

2)and also i am seeing REM huristics is creating new planned order when running the hurisrics each time with out change in requirement-pl suguest