X-Git-Url: https://git.octo.it/?a=blobdiff_plain;ds=sidebyside;f=doc%2Frrdgraph_data.pod;h=04d976174b4a679cf0eac31a2589d99f6d3e3e6e;hb=d839737b6b8dfad9bd6336a42041e9b5067dc870;hp=e8b2c6719d3ecebb658bc0bd72c059b9745d2f7d;hpb=cb092381724e4ba8a1f18712fefc541a3d370f99;p=rrdtool.git

diff --git a/doc/rrdgraph_data.pod b/doc/rrdgraph_data.pod
index e8b2c67..04d9761 100644
--- a/doc/rrdgraph_data.pod
+++ b/doc/rrdgraph_data.pod
@@ -19,6 +19,9 @@ useful information such as maximum, minimum etcetera. Two of the
 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, -,_> and a maximum length of 255 characters.
+
 =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>>][:reduce=I<E<lt>B<CF>E<gt>>]
@@ -68,6 +71,9 @@ 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>