Objectives
User-specific requirements can be considered with 
Personal Settings. This way, each user can set their own default settings and specify that the document overview is set automatically when the transaction is started.
In addition, a help function can be displayed like the document overview. You can display or hide this help area by choosing 
(Help). If the help area is open, you can work in the transaction at the same time.
If you have a procurement process with preceding documents for the purchase order, you must create the purchase order with reference to one of these preceding documents. If reference is made to a purchase requisition, an RFQ, or a contract, then the item data and any existing header data is copied from the preceding document to the purchase order. This reduces the required entry effort and therefore reduces possible entry errors. You can change most of the copied data in the purchase order, if necessary.
In the transaction ME21N, the document overview makes it easy to create a purchase order with reference.
If you have selected the preceding documents in the document overview, then select the document or the document items and choose 
(Adopt). You can also move the selected documents into the shopping cart by dragging and dropping them.
Hint
For each item, the system updates the document and item number of the template item in the purchase order. You can therefore see whether the PO item was created with reference to another document item. You can find the exact number of the referenced document item for each PO item in the item overview.
To create a purchase order with reference to another document, you can also enter the number of the document and the number of the item directly in the corresponding fields in the item overview.
In the document overview, you can display the different purchasing documents that you require for your daily work (purchase orders, purchase requisitions, RFQs, and contracts). At the same time, you can process a purchase order or purchase requisition in the right screen area.
To display a purchase order or purchase requisition from the document overview, double-click the relevant item. For the other purchasing documents (an RFQ, scheduling agreement, or contract) it is not possible to call the display transaction by the way of double-clicking the document number in the document overview.
You use the selection variant to decide which documents to select. For example, on the selection screen you can restrict the vendor, material, and period of the document creation. If you want to select only the purchase orders or the purchase requisitions that you created yourself, you can use the selection variants My purchase orders and My purchase requisitions. You do not need to enter any further selection values here. Specify the selection period for these two variants in your personal settings.
In the breakdown, specify the criteria to be used for sorting the selected documents.
Then you can use the layout to determine the data to be displayed for the documents. This is described in the following section in more detail.
Hint
You can select the purchase requisition items to be converted according to several criteria, such as the purchasing group, the purchasing organization, the MRP controller, and the vendor. You can also decide that the system is to create release orders for contracts. During selection, purchase requisition items with assigned contracts are also considered.
Decide how the system groups the purchase requisition items into purchase orders. You can specify, for example, that a new purchase order is created for each purchasing group, plant, or delivery date.
If an item in a purchase requisition contains errors, it cannot be converted into a purchase order. An item has errors if the master data is wrong or incomplete (for example, if the vendor is blocked for purchasing). Input data could also be missing (for example, the account assignment from the account assignment category Unknown field, or the tax code for the evaluated receipt settlement).
Before you execute the automatic generation of a purchase order, determine whether or not incorrect items have been left out during conversion.
Exclude items with errors:
The system creates purchase orders from all correct purchase requisition items, according to your requirements. You can see the errors in a log and process the incorrect items again.
Do not exclude items with errors:
The system creates all purchase orders that can be created by grouping together correct purchase requisition items only, according to your requirements. All other purchase requisition items are not converted.
If, for example, the system has to group together ten purchase requisition items into one purchase order and one of these items has an error, the purchase order could not be created. None of the ten items are then ordered. This is useful if the contents of the purchase requisition items should also be in the purchase order.