The document type controls how a document is stored and edited. You therefore need to make the Customizing settings relevant to the document type.SAP supplies the Document Types Customizing Wizard to help create new document types. You can also use the Document Types Customizing Wizard repeatedly to create new document types when the system is in operation. It is often necessary to directly access individual records in a data structure. This is done using unique keys. Number ranges are used to assign numbers to individual database records for a commercial object, to complete the key. Such numbers are e.g. order numbers or material master numbers.The R/3 number range management also monitors the number status, so that numbers which have already been issued are not re-issued.