Archiving materials

Hi all

I wanna archive some materials which are not used anymore. First of all, using SE38, I executed program MMREO001 and then, while running MMREO050 I face this error:

"Structure IBCOMP is not known in the ABAP Dictionary

    Message no. BA123

Diagnosis

    Structure IBCOMP is contained in the definition of archiving object or

    archiving class MM_MATNR. This structure is not recognized by the ABAP

    Dictionary in the SAP System.

System Response

    Archiving is terminated.

Procedure

    If you are using an SAP archiving object, report this information to

    SAP. If you are using a customer archiving object or a customer

    archiving class, remove structure IBCOMP from the definition of

    archiving object or archiving class MM_MATNR ."

Can anyone help me?

Regards,

Mona