Activating Availability Control Online 
In the budget profile you selected activation type two for availability control (background activation). You can now activate availability control in advance for one particular project online.
You can therefore activate availability control for a project before the usage level has been reached for background processing, or before the next background run.
In The Project System (Same Procedure For Internal Orders)
You activate availability control online as follows:
The system confirms activation with a message.

Availability control is activated only when you next Save or make a Check. After activation, each posting that follows is checked for availability.

If you now want to reduce the budget (for example), and the allotted funds thus exceed the tolerance limit in the availability control, you are notified when you check or save the budget.