Serial numer error: Serial numbers already assigned to this material

Hi,

A serial number has been assigned to a material. Now i want to change the serial number profile in the material master. I am getting "Serial number already assigned to this material" error message. I have got some link regarding this issue to execute a program RISERNR9, but i am not sure what exactly it does.

Please suggest how can I change the serial number profile in material master.

Thanks in advance.

Satya