(Alpha and I64 only.) The Return Virtual Memory Statistics
    routine returns to its caller one of six statistics available
    from calls to LIB$GET_VM_64 and LIB$FREE_VM_64, as well as
    LIB$GET_VM_PAGE_64 and LIB$FREE_VM_PAGE_64. Unlike LIB$SHOW_
    VM_64, which formats the values for output and displays them on
    SYS$OUTPUT, LIB$STAT_VM_64 returns the statistic in the value-
    argument argument. Only one of the statistics is returned by each
    call to LIB$STAT_VM_64.
    Format
      LIB$STAT_VM_64  code ,value-argument
1 – Returns
    OpenVMS usage:cond_value
    type:         longword (unsigned)
    access:       write only
    mechanism:    by value
2 – Arguments
 code
    OpenVMS usage:quadword_signed
    type:         quadword integer (signed)
    access:       read only
    mechanism:    by reference
    Code specifying which statistic is to be returned. The code
    argument contains the address of a signed quadword integer that
    is this code.
    Code  Statistic
    1     Number of successful calls to LIB$GET_VM_64
    2     Number of successful calls to LIB$FREE_VM_64
    3     Number of bytes allocated by LIB$GET_VM_64 but not yet
          deallocated by LIB$FREE_VM_64
    5     Number of calls to LIB$GET_VM_PAGE_64
    6     Number of calls to LIB$FREE_VM_PAGE_64
    7     Number of Alpha or I64 pagelets allocated by LIB$GET_VM_
          PAGE_64 but not yet deallocated by LIB$FREE_VM_PAGE_64
    Note that it is invalid to omit code or to give a code of 0 or 4.
 value-argument
    OpenVMS usage:user_arg
    type:         quadword (unsigned)
    access:       write only
    mechanism:    by reference
    Value of the statistic returned by LIB$STAT_VM_64. The value-
    argument argument contains the address of an unsigned quadword
    integer that is this value.