@@ -52,7 +64,7 @@ own manual page.
A-Z, a-z, 0-9, -,_ and a maximum length of 255 characters.
When picking variable names, make sure you do not choose a name that is already taken by an RPN operator. A safe bet it to use lowercase or -mixedcase names for variables since operators will always be in uppercase.
+mixed case names for variables since operators will always be in uppercase.
--start end-8days8hours).
If consolidation needs to be done, the CF of the RRA specified in the
-DEF itself will be used to reduce the data density. This behaviour can
+DEF itself will be used to reduce the data density. This behavior can
be changed using :reduce=<CF>. This optional parameter
specifies the CF to use during the data reduction phase.
Example:
@@ -114,6 +126,31 @@ the script, just as if it were generated by a DEF instruction.<
At some point in processing, RRDtool has gathered an array of rates +ready to display.
+CDEF works on such an array. For example, CDEF:new=ds0,8,* +would multiply each of the array members by eight (probably +transforming bytes into bits). The result is an array containing the +new values.
+VDEF also works on such an array but in a different way. For +example, VDEF:max=ds0,MAXIMUM would scan each of the array members +and store the maximum value.
++
+Use CDEF to transform your data prior to graphing. In the above +example, we'd use a CDEF to transform bytes to bits before +graphing the bits.
+You use a VDEF if you want max(1,5,3,2,4) to return five which +would be displayed in the graph's legend (to answer, what was the +maximum value during the graph period).
+If you want to apply 'complex' operations to the result of a VDEF you have +to use a CDEF again since VDEFs only look like RPN expressions, they aren't +really.
++
+the rrdgraph manpage gives an overview of how rrdtool graph works. the rrdgraph_data manpage describes DEF,CDEF and VDEF in detail.