Not possible to delete MRP area &1, as it is assigned to material &2

What causes this issue?

MRP area &V1& is assigned to material &V2& and therefore cannot be
deleted.

System Response

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

How to fix this error?

Reorganize the MRP data using the archiving object MM_MATNR.

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.