*COMDECK SCIDDCLS 
        BEGIN 
        ITEM SCHNUM   U(00,00,12);     # NO. OF SCHEMA IDS IN THE TABLE#
                                       # BITS 12-23 ARE UNUSED         #
        ITEM SCHPRIOR U(00,24,18);     # PTR TO PRIOR SID MM BLOCK     #
        ITEM SCHNEXT  U(00,42,18);     # PTR TO NEXT SID MM BLOCK      #
                                       # BITS 0-47 ARE UNUSED          #
        ITEM SCHID    U(00,48,12);     # SCHEMA IDENTIFIER             #
        END 
