[rrd-users] Adding two VDEF values together

Yannick Marquet itcsoft54 at yahoo.fr
Sat Feb 23 14:12:21 CET 2013

>> So, a VDEF is a set of data and a CDEF is a single value, but a TOTAL
>> will be a single value?
no, it is opposite :

CDEF and DEF, are series of values, number of value depends on step 
parameter an the consolidation function (/CF/).
VDEF is a single value.

You cant use CDEF without DEF or CDEF variables because you can't 
calculate number of value needed for series.

Le 21/02/2013 22:37, Alex van den Bogaerdt a écrit :
>> I was trying to do something which I thought was fairly simple, but I
>> keep on getting the following error:
>> "ERROR: rpn expressions without DEF or CDEF variables are not supported"
>> In the most simplest form, I am trying to do the following:
>> DEF:A=<rrdfile>:A:AVERAGE
>> DEF:B=<rrdfile>:B:AVERAGE
>> So, a VDEF is a set of data and a CDEF is a single value, but a TOTAL
>> will be a single value?
> VDEF support is currently very limited. What you are trying to do is,
> indeed, not possible this way.
>> I am trying to take two totals and add them together - seems fairly
>> common to want to do this?
> The workaround is to do your math inside a CDEF, and then find the total.
> VDEF:total=c,TOTAL
> hth
> alex
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