Diagnosis
You want to use mass change to replace a material in BOMs with anothermaterial. This is only possible if the old and new material have thesame issue unit.
The same applies to the base units of the two materials.

Procedure
You have two options:
Enter another material which has the same issue unit as the material tobe replaced.
Check whether the units of measure of the new material need to bechanged.
A material master can only be changed in consultation with theresponsible area.