Release procedure for purchase orders is used to control purchase of goods by way of authorization required by managers before the PO is actually sent to the vendor.
You can implement release procedures using many types of characteristics whose values are linked to data in the database tables. These values in characteristics work as a control parameter and determine flow and path the release procedure will take for the process of releasing the PO. The most obvious control parameter is the PO value in dollars. For POs where the purchase value is not significant need not be directed for authorization and can be sent to the vendor without any need of authorization. However for POs where the PO value is significant, must be sent for authorization and only after approval should be sent to the vendor. To implement this, you need to find out which field in which database table stores the PO value. Then using characteristics you can check if this PO value is greater or lesser than the PO value limit for authorization. If the PO value is more than this limit then the PO must be sent for approval. Only after approval, it can be sent to the vendor.
Other control parameters for PO release include purchase organization, purchase group, company code, document type etc. For example, POs which need to be processed by a particular purchase group need to be released only after authorization. In this case, a characteristic value must be present which can be compared with the purchase group number and if they match then the release strategy for the PO should kick in. These POs then must be released before they are sent to the vendor.
You can use characteristic values which can be matched with some data which is part of the PO document header. You can not use any characteristic value which can be matched with some value at the item level. For example a plant is part of PO line item and is not part of PO header. The PO release strategy works only at the header level. This means you can not release individual PO line items. The PO must be released at the header level. So if you want that a PO for a certain plant must be released prior to sending it to the vendor does not work in SAP. there is no such functionality in SAP. Though if the material you are purchasing is coming from a plant in your company then this supplying plant can be checked and used for a release strategy. In inter company material transfers, the supplying plant comes at the header level in a PO and thus is available for check.