Material demand issued refers to the design object additional parts that have been issued.
Reserving means allocating the needed material situated in one or several inventory locations. You can either reserve all the material at the same time or perform a manual reservation line-by-line. When doing a manual reservation, you can specify a quantity to reserve and define a specific inventory location. Serial numbered parts should be manually reserved. You cannot reserve a higher quantity than the quantity available in stock.
When the parts are reserved, the line changes from the Release status to the Reserved status (the header will still display the Released status). Once a line is reserved, it cannot be deleted. Deletion can be done only for lines in the Planned or Released status.
Issuing material means picking the ordered material from an inventory location. The parts need to be reserved before you are allowed to issue the material. You can either issue all the material at the same time or perform a manual issue, for example, you can issue a lesser quantity than reserved or issue line-by-line. If all the parts have been issued, the status changes to Closed. If a partial issue is done, the status will be Partially Delivered. You can close the line if you decide that you do not need the remaining quantity.
Once a line is issued, it cannot be deleted. Deletion can be done only for lines in the Planned or Released status.
Un-issuing means returning the unused parts back to an inventory location. This operation will not lead to any status change. The quantity returned cannot exceed the issued quantity.