/ALLOCLASS=number

    This qualifier is not required and defaults to 99. It is only
    allowed for SHARED memory type disks. Note that associating a
    particular controller letter with a specific allocation class
    is valid for all time! All time means as long as the shared
    memory section exists or the MDRECOVER.DAT file exists. Selecting
    an allocation class equal to the node's allocation class for
    shared memory disks is not allowed.