new command rrdtool xport integrated

[rrdtool.git] / doc / rrdupdate.pod

diff --git a/doc/rrdupdate.pod b/doc/rrdupdate.pod
index bc4e902..d35b35b 100644 (file)
--- a/doc/rrdupdate.pod
+++ b/doc/rrdupdate.pod
@@ -9,6 +9,7 @@ rrdtool update - Store a new set of values into the rrd
 B<rrdtool> B<update> I<filename> 
 S<[B<--template>|B<-t> I<ds-name>[B<:>I<ds-name>]...]> 
 S<B<N>|I<timestamp>B<:>I<value>[B<:>I<value>...]> 
+S<I<at-timestamp>B<@>I<value>[B<:>I<value>...]> 
 S<[I<timestamp>B<:>I<value>[B<:>I<value>...] ...]>
 
 =head1 DESCRIPTION
@@ -25,21 +26,34 @@ The name of the B<RRD> you want to update.
 
 =item B<--template>|B<-t> I<ds-name>[B<:>I<ds-name>]...
 
-by default, the update function expects the data input in the order,
-the data sources are defined in the RRD. This is not very error
-resistant, as you might be sending the wrong data into a RRD.
+by default, the B<update> function expects the data input in the order
+the data sources are defined in the RRD, excluding any COMPUTE data sources 
+(i.e. if the third data source B<DST> is COMPUTE, the third input value
+will be mapped to the fourth data source in the B<RRD>). This is not very
+error resistant, as you might be sending the wrong data into a RRD.
 
 The template switch allows you to specify which data sources you are
 going to update and in which order. If the data sources specified in
 the template are not available in the rrd file, the update process
 will abort with an error message.
 
+While it appears possible with the template switch to update data sources
+asynchronously, B<RRDtool> implicitly assigns non-COMPUTE data sources missing
+from the template the I<*UNKNOWN*> value. 
+
+Do not specify a value for a COMPUTE B<DST> in the B<update> function. If
+this is done accidently (and this can only be done using the template switch),
+B<RRDtool> will ignore the value specified for the COMPUTE B<DST>.
+
 =item B<N>|I<timestamp>B<:>I<value>[B<:>I<value>...]
 
 The data used for updating the RRD was acquired at a certain time. This
 time can either be defined in seconds since 1970-01-01. Or by using the
 letter 'N' the update time is set to be the current time. Negative time
 values are subtracted from the current time.
+An AT_STYLE TIME SPECIFICATION (see the I<rrdfetch> documentation) may
+also be used by delimiting the end of the time specification with the '@' character
+instead of a ':'.
 Getting the timing right to the second is especially
 important when you are working with data-sources of type B<COUNTER>,
 B<DERIVE> or B<ABSOLUTE>. 
@@ -51,7 +65,7 @@ B<U> (eg. N:0.1:U:1) can be defined.
 
 The format of the value acquired from the data source is dependent of the
 data source type chosen. Normally it will be numeric, but the data acquisition
-modules my impose their very own parsing of this parameter as long as the colon
+modules may impose their very own parsing of this parameter as long as the colon
 (B<:>) remains the data source value separator.
 
 =back