The Return Virtual Memory Statistics routine returns to its
    caller one of six statistics available from calls to LIB$GET_
    VM/LIB$FREE_VM and LIB$GET_VM_PAGE/LIB$FREE_VM_PAGE. Unlike
    LIB$SHOW_VM, which formats the values for output and displays
    them on SYS$OUTPUT, LIB$STAT_VM returns the statistic in the
    value-argument argument. Only one of the statistics is returned
    by each call to LIB$STAT_VM.

    Format

      LIB$STAT_VM  code ,value-argument