X-Git-Url: https://git.octo.it/?p=rrdtool.git;a=blobdiff_plain;f=doc%2Frrdgraph_data.pod;h=c26868f0e509ffe00559f52922ae16a770d9daf2;hp=c57b2c356d04c35527d7a8ffe4160c0f2c4e3fec;hb=22129bb15a8ad204cf8a5e88e8834ec0b51908c0;hpb=9b3f8a096b6202b9bd580586476660933c7f913f

diff --git a/doc/rrdgraph_data.pod b/doc/rrdgraph_data.pod
index c57b2c3..c26868f 100644
--- a/doc/rrdgraph_data.pod
+++ b/doc/rrdgraph_data.pod
@@ -20,7 +20,11 @@ instructions use a language called B<RPN> which is described in its
 own manual page.
 
 Variable names (I<vname>) must be made up strings of the following characters
-C<A-Z, a-z, 0-9, -,_> with a maximum length of 255 characters.
+C<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.
 
 =head1 DEF
 
@@ -71,6 +75,9 @@ elements.
 
 Example: C<VDEF:avg=mydata,AVERAGE>
 
+Note that currently only agregation functions work in VDEF rpn expressions.
+Patches to change this are welcome.
+
 =head1 CDEF
 
 B<CDEF>:I<vname>=I<RPN expression>
@@ -94,6 +101,6 @@ Make sure to read L<rrdgraph_examples> for tipsE<amp>tricks.
 
 =head1 AUTHOR
 
-Program by Tobias Oetiker E<lt>oetiker@ee.ethz.chE<gt>
+Program by Tobias Oetiker E<lt>tobi@oetiker.chE<gt>
 
 This manual page by Alex van den Bogaerdt E<lt>alex@ergens.op.het.netE<gt>