LNMPHASHTBL sets the size of the process logical name hash table.
    Logical names are hashed using a function of the name length
    and contents. The LNMPHASHTBL parameter determines the number
    of entries for process-private logical names. The recommended
    setting is the average number of process-private logical names.
    Note that the hashed values are rounded up to the nearest power
    of 2.

    LNMPHASHTBL has the GEN attribute.