/ENABLE=HBMM
       /ENABLE=SPLIT_READ_LBNS

    Enables host-based minimerge (HBMM) on the specified shadow set
    or across the entire cluster if an applicable HBMM policy exists.

    /ENABLE=SPLIT_READ_LBNS logically divides the shadow set members
    having the same read cost into equal groups of Logical Block
    Numbers (LBNs). When a virtual unit performs a read, it does so
    by reading from the corresponding LBN group. This results in the
    maximum usage of the controller read-ahead cache. To learn more
    about HBMM policies and their application, see the HP Volume
    Shadowing for OpenVMS manual.