We are currently using the alternative product numbers in SCM, instead of entering them directly into SCM we have created an additiona table in ERP where we store them and CIF them to the product master in SCM.

As ERP is now are master for alternative product numbers and NOT SCM. I am wondering if we can make these fields "display" only, but I see no place in customizing where I can do this.

Here is a clue :

In customizing, you can define new atributes (field name ATT*) for location, product or even location product master (tables /SAPAPO/LOC, /SAPAPO/MATKEY and /SAPAPO/MATLOC).

See in customizing option : APO --> Master data --> Maintain freely-definable attributes, it's really easy.

Once you created a new attribute for a product location for example, the extra field will appear in a new folder named "extra". It will be usable for display or even in queries, advanced macros and so on...

You can use the extra fields/attributes in Product Master to set up alternative Product numbers. One would have to check with Security folks on how you can make that extra field non-editable for roles/authorizations. I am sure there are levers around Product Master authorization object to set this up. CIF user exit can populate the extra attribute field of Product Master. 

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