The Safety Stock Quantity field is used in the following ways for planning calculations when the projected available balance is below the safety stock quantity:

• An order proposal that is backward scheduled from the due date of the requirement that caused the deficit in the projected available balance is created.
  
• The order proposal quantity brings the projected available balance up to at least the level that is specified in the Safety Stock Quantity field.
  

  Note
  The final order proposal quantity may be adjusted because of additional requirements in the time bucket, the effects of the reordering policy, and the Minimum Order Quantity, Maximum Order Quantity, and Order Multiple quantity modifier fields.

The safety stock quantity must always be below the reorder point.

If you leave the field blank, then the safety stock quantity for the item is set to zero. If you enter a negative number in the field, then the value is ignored.

Although a safety stock quantity is set aside to compensate for fluctuations, the planning system may consume from it to meet a demand that could otherwise not be fulfilled on its due date. In that case, the planning system ensures that the safety stock is replaced by suggesting an exception supply order to replenish the safety stock quantity on the date that it is consumed. This planning line displays an exception warning to explain that the safety stock has been partly or fully consumed and must be replenished.

Reference