How to prevent planned orders in one Supply Plan from being released?

Summary:

How to prevent planned orders in the Supply Plan from being released?

Content (required):

We have two Supply Plans(Type Production) in our system. The first supply plan will have external forecast as input have system generated planned orders after demand/supply netting and finally these planned orders will be released to create work orders.

The second supply plan is a repository for manual uploaded planned orders to mimic the detailed production schedule from Contract manufacturer. This plan is just for information and system should not allow the planners to release planned orders from this plan.

Both these plans will be comprising the same items and organization however I want system not to allow release of planned orders from the second plan.