-=include name
+=head1 NAME
-=head1 SYNOPSYS
+rrdgraph_data - preparing data for graphing in rrdtool graph
-B<DEF:>I<E<lt>vnameE<gt>>=I<E<lt>rrdfileE<gt>>:I<E<lt>ds-nameE<gt>>:I<E<lt>CFE<gt>>[:step=I<E<lt>stepE<gt>>][:start=I<E<lt>timeE<gt>>][:end=I<E<lt>timeE<gt>>]
+=head1 SYNOPSIS
+
+B<DEF:>I<E<lt>vnameE<gt>>=I<E<lt>rrdfileE<gt>>:I<E<lt>ds-nameE<gt>>:I<E<lt>CFE<gt>>[:step=I<E<lt>stepE<gt>>][:start=I<E<lt>timeE<gt>>][:end=I<E<lt>timeE<gt>>][:reduce=I<E<lt>B<CF>E<gt>>]
B<VDEF>:I<vname>=I<RPN expression>
These three instructions collect the data out of the B<RRD> files,
optionally altering it (think of a bytes to bits conversion) and
if desired you can define variables containing useful information
-such as maximum, mininimum etcetera. Two of the instructions use
+such as maximum, minimum etcetera. Two of the instructions use
a language called B<RPN> which is described in its own manual page.
=head1 DEF
-B<DEF:>I<E<lt>vnameE<gt>>=I<E<lt>rrdfileE<gt>>:I<E<lt>ds-nameE<gt>>:I<E<lt>CFE<gt>>[:step=I<E<lt>stepE<gt>>][:start=I<E<lt>timeE<gt>>][:end=I<E<lt>timeE<gt>>]
+B<DEF:>I<E<lt>vnameE<gt>>=I<E<lt>rrdfileE<gt>>:I<E<lt>ds-nameE<gt>>:I<E<lt>CFE<gt>>[:step=I<E<lt>stepE<gt>>][:start=I<E<lt>timeE<gt>>][:end=I<E<lt>timeE<gt>>][:reduce=I<E<lt>B<CF>E<gt>>]
This command fetches data from an B<RRD> file. The virtual name
I<vname> can then be used throughout the rest of the script. By
default, an B<RRA> which contains the correct consolidated data
at an appropriate resolution will be chosen. The resolution can
-be overriden with the L<--step|rrdgraph/item_Time> option.
-The resolution can again be overriden by specifying the B<step size>.
+be overridden with the L<--step|rrdgraph/item_Time> option.
+The resolution can again be overridden by specifying the B<step size>.
The time span of this data is the same as for the graph by default,
you can override this by specifying B<start and end>. Remember to
escape colons in the time specification!
image with width 400 and time span 400*1800 seconds (use appropriate
start and end times, such as C<--start end-8days8hours>).
+If consolidation needs to be done, the B<CF> of the B<RRA> specified in the
+B<DEF> itself will be used to reduce the data density. This behaviour can
+be changed using C<:reduce=I<E<lt>B<CF>E<gt>>>. This optional parameter
+specifies the B<CF> to use during the data reduction phase.
+
Example:
DEF:ds0=router.rrd:ds0:AVERAGE
this I<vname> in another B<RPN> expression, you are effectively
inserting its value just as if you had put a number at that place.
The variable can also be used in the various graph and print
-elements. I<Not yet implemented:> [ Everywhere you can insert a
-number, you can also use the B<VDEF> (provided that it is set of course) ]
+elements.
Example: C<VDEF:avg=mydata,AVERAGE>
Example: C<CDEF:mydatabits=mydata,8,*>
-=include see_also
+=head1 SEE ALSO
+
+L<rrdgraph> gives an overview of how B<rrdtool graph> works.
+L<rrdgraph_data> describes B<DEF>,B<CDEF> and B<VDEF> in detail,
+L<rrdgraph_rpn> describes the B<RPN> language used in the B<?DEF> statements,
+L<rrdgraph_graph> page describes all of the graph and print functions.
+
+Make sure to read L<rrdgraph_examples> for tipsE<amp>tricks.
+
+=head1 AUTHOR
+
+Program by Tobias Oetiker E<lt>oetiker@ee.ethz.chE<gt>
+
+This manual page by Alex van den Bogaerdt E<lt>alex@ergens.op.het.netE<gt>