number-of-pagelets

    Specifies the number of pagelets (512-byte units) to be allocated
    for the image I/O segment. By default, the operating system uses
    the value set by the IMGIOCNT system parameter to determine the
    size of the image I/O space.

 [NO]P0BUFS

    By default, the operating system allocates the I/O segment in
    the P1 region of the process space and, if additional space is
    needed, at the end of the P0 region. If you specify NOP0BUFS, you
    deny OpenVMS RMS additional pages in the P0 region.