Material number is sap determines how the material will be numbered. You can create it by internal assignment or external assignment. Followings are the list how to define these for a material.
Material Number field
To create it you need to use transaction code OMSL or path;
SPRO > IMG > Logistics > General > Material Master > Basic Settings > Define Output format for material number
Through this transaction you can create length of your material no. Before entering this No. you must first decide this with the business process owner. If they have a different existing material number series and they want it to be used in sap then you need work as per there requirements.
In material number template you can configure it by adding special character in between it. Underscore can not be entered in between the material number. Other than underscore you can use any special character.
What is lexicographical?
If you select this indicator while creating your material number range SAP will only defines and assigns numerical number created internally or externally.
If you do not set this indicator and in the material number length field you select 10 then sap will define your material number in 10 letters starting with zeros. For example if a user enter it as 1234 then sap creates it as 0000001234.
If you set this indicator then material number will be the one that you entered into sap. If you have entered it as 1234 then system creates it as 1234. If you enter it as 01234 then SAP will it as 01234. However if you do not enter it and system creates it internally then it will add with zeros in front even though this indicator is set.
You can not change this setting once materials with this setting are already created. You have to take this decision very carefully at the time of planning so that changes to it will not arise.
What is leading Zeros field
If you set this indicator then sap will add leading zeros to the material number created. If you create material as 1234 then system will add leading zeros to it as 0000001234 (assuming the length has been set to 10).
After the creation of material number field your next step is to creation of material number range. To create number range you need to use transaction code MMNR or following path;
SPRO > IMG > Logistics > General > Material Master > Basic Settings > Material Type > Define Number Ranges for material type
Here you enter a range of numbers and define whether then it will be system defined or will be entered by the user.
If you select the field “ext” then the user has to enter the material number manually or else system will assign it sequentially to the material master created in sap.
The current number that you see in the configuration screen will become the next material when you created a material in sap. After the current one is assigned the next one will become the current number and will be ready to assign.
The best thing in internal assignment is you will have audit trail of each and every material in sap. And all the materials will be created sequentially.