[rrd-users] Adding two VDEF values together

Alex van den Bogaerdt alex at vandenbogaerdt.nl
Thu Feb 21 22:37:52 CET 2013

> 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.



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