When the options are added, you will need to save and synchronize the changes before restarting the application server to put the changes in effect.
When tuning for generational garbage collection, the simplest approach is to treat the nursery space as a new Java heap area, in addition to the Java heap area used in the non-generational case. The Java heap for the non-generational case therefore becomes the tenured heap.
This approach is conservative: the expectation is that the occupancy of the tenured heap will drop as a result of introducing the nursery, but it provides a safe starting point, especially in the case of a migration from a non-generational policy. When the occupancy of the tenure heap after global (full) collections can be monitored, the size can then be adjusted as described earlier: