[MRP] Planning Active

Excerpt from Oarcle Online Help for Define Sourcing Rules:
7. Enter an allocation percentage for each shipping organization. Allocation percentage includes the number of planned orders issued to the part for the entire the planning horizon. Your total allocation may not exceed 100.

If the allocation percentage for all the shipping organizations included within a range of effectivity dates equals 100, Planning Active is checked. If the sourcing rule is not planning active, the planning process will not use the rule to assign planned orders.

Note: You cannot set the allocation percentage to less than or greater than 100 for sourcing rules that are already assigned in assignment sets.

The Planning Active field is not editable by design. FYI, I tested the last note "Note: You cannot set...", it is not true.