VMS Help Sys Parameters, IMGIOCNT  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    IMGIOCNT specifies the default number of pages of image I/O
    address space to be allocated for the image activator if not
    specified at program link time.

    This special parameter is used by Compaq and is subject to
    change. Do not change this parameter unless Compaq recommends
    that you do so.