/sys$common/syshlp/helplib.hlb Sys Parameters, GH_RSRVPGCNT  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    GH_RSRVPGCNT specifies the number of pages in the resident image
    granularity hint region that the Install utility can use after
    the system has finished booting.

    If bit 2 of the LOAD_SYS_IMAGES parameter is set, the image
    LDR$WRAPUP releases all unused pages in the granularity hint
    region at the the end of system startup. The unused pages of the
    resident image granularity hint region are either reserved for
    future use, or given back to the free memory list.

    GH_RSRVPGCNT specifies the number of pages that LDR$WRAPUP
    attempts to leave in the resident image granularity hint region.
    If the GH_RSRVPGCNT number of pages is larger than the unused
    pages in the granularity hint region, the region is not expanded
    to accommodate the number of pages requested.

    GH_RSRVPGCNT is a FEEDBACK attribute parameter.