=head1 NAME

rrdtune - Modify some basic properties of a Round Robin Database

=head1 SYNOPSIS

B<rrdtool> B<tune> I<filename>
S<[B<--heartbeat>|B<-h> I<ds-name>:I<heartbeat>]>
S<[B<--minimum>|B<-i> I<ds-name>:I<min>]>
S<[B<--maximum>|B<-a> I<ds-name>:I<max>]>
S<[B<--data-source-type>|B<-d> I<ds-name>:I<DST>]>
S<[B<--data-source-rename>|B<-r> I<old-name>:I<new-name>]>
S<[B<--deltapos>|B<-p> I<scale-value>]>
S<[B<--deltaneg>|B<-n> I<scale-value>]>
S<[B<--failure-threshold>|B<-f> I<failure-threshold>]>
S<[B<--window-length>|B<-w> I<window-length>]>
S<[B<--alpha>|B<-x> I<adaption-parameter>]>
S<[B<--beta>|B<-y> I<adaption-parameter>]>
S<[B<--gamma>|B<-z> I<adaption-parameter>]>
S<[B<--gamma-deviation>|B<-v> I<adaption-parameter>]>
S<[B<--smoothing-window>|B<-s> I<fraction-of-season>]>
S<[B<--smoothing-window-deviation>|B<-S> I<fraction-of-season>]>
S<[B<--aberrant-reset>|B<-b> I<ds-name>]>
S<[B<--step>|B<-t> I<newstep>]>
S<[B<--daemon>|B<-D> I<address>]>
S<[B<DEL:>I<ds-name>]>
S<[B<DS:>I<ds-spec>]>
S<[B<DELRRA:>I<index>]>
S<[B<RRA:>I<rra-spec>]>
S<[B<RRA#>I<index>:[+-=]<number>]>

=head1 DESCRIPTION

The tune option allows you to alter some of the basic configuration
values stored in the header area of a Round Robin Database (B<RRD>).

One application of the B<tune> function is to relax the
validation rules on an B<RRD>. This allows you to fill a new B<RRD> with
data available in larger intervals than what you would normally want
to permit. Be very careful with tune operations for COMPUTE data sources.
Setting the I<min>, I<max>, and  I<heartbeat> for a COMPUTE data source
without changing the data source type to a non-COMPUTE B<DST> WILL corrupt
the data source header in the B<RRD>.

A second application of the B<tune> function is to set or alter parameters
used by the specialized function B<RRAs> for aberrant behavior detection.

Still another application is to add or remove data sources (DS) or 
add / remove or alter some aspects of round-robin archives (RRA). These operations 
are not really done in-place, but rather generate a new RRD file internally and 
move it over the original file. Data is kept intact during theses operations.
For even more in-depth modifications you may review the 
S<B<--source>> and S<B<--template>> options of the B<create> function which  
allow you to combine multiple RRD files into a new one and which is even more clever 
in what data it is able to keep or "regenerate".

=over 8

=item I<filename>

The name of the B<RRD> you want to tune.

=item S<B<--heartbeat>|B<-h> I<ds-name>:I<heartbeat>>

modify the I<heartbeat> of a data source. By setting this to a high
value the RRD will accept things like one value per day.

=item S<B<--minimum>|B<-i> I<ds-name>:I<min>>

alter the minimum value acceptable as input from the data source.
Setting I<min> to 'U' will disable this limit.

=item S<B<--maximum>|B<-a> I<ds-name>:I<max>>

alter the maximum value acceptable as input from the data source.
Setting I<max> to 'U' will disable this limit.

=item S<B<--data-source-type>|B<-d> I<ds-name>:I<DST>>

alter the type B<DST> of a data source.

=item S<B<--data-source-rename>|B<-r> I<old-name>:I<new-name>>

rename a data source.

=item S<B<--deltapos>|B<-p> I<scale-value>>

Alter the deviation scaling factor for the upper bound of the
confidence band used internally to calculate violations for the
FAILURES B<RRA>. The default value is 2. Note that this parameter is
not related to graphing confidence bounds which must be specified as a
CDEF argument to generate a graph with confidence bounds. The graph
scale factor need not to agree with the value used internally by the
FAILURES B<RRA>.

=item S<B<--deltaneg>|B<-n> I<scale-value>>

Alter the deviation scaling factor for the lower bound of the confidence band
used internally to calculate violations for the FAILURES B<RRA>. The default
value is 2. As with B<--deltapos>, this argument is unrelated to the scale
factor chosen when graphing confidence bounds.

=item S<B<--failure-threshold>|B<-f> I<failure-threshold>>

Alter the number of confidence bound violations that constitute a failure for
purposes of the FAILURES B<RRA>. This must be an integer less than or equal to
the window length of the FAILURES B<RRA>. This restriction is not verified by
the tune option, so one can reset failure-threshold and window-length
simultaneously. Setting this option will reset the count of violations to 0.

=item S<B<--window-length>|B<-w> I<window-length>>

Alter the number of time points in the temporal window for determining
failures. This must be an integer greater than or equal to the window
length of the FAILURES B<RRA> and less than or equal to 28. Setting
this option will reset the count of violations to 0.

=item S<B<--alpha>|B<-x> I<adaption-parameter>>

Alter the intercept adaptation parameter for the Holt-Winters
forecasting algorithm. This parameter must be between 0 and 1.

=item S<B<--beta>|B<-y> I<adaption-parameter>>

Alter the slope adaptation parameter for the Holt-Winters forecasting
algorithm. This parameter must be between 0 and 1.

=item S<B<--gamma>|B<-z> I<adaption-parameter>>

Alter the seasonal coefficient adaptation parameter for the SEASONAL
B<RRA>. This parameter must be between 0 and 1.

=item S<B<--gamma-deviation>|B<-v> I<adaption-parameter>>

Alter the seasonal deviation adaptation parameter for the DEVSEASONAL
B<RRA>. This parameter must be between 0 and 1.

=item S<B<--smoothing-window>|B<-s> I<fraction-of-season>>

Alter the size of the smoothing window for the SEASONAL B<RRA>. This must
be between 0 and 1.

=item S<B<--smoothing-window-deviation>|B<-S> I<fraction-of-season>>

Alter the size of the smoothing window for the DEVSEASONAL B<RRA>. This must
be between 0 and 1.

=item S<B<--aberrant-reset>|B<-b> I<ds-name>>

This option causes the aberrant behavior detection algorithm to reset
for the specified data source; that is, forget all it is has learnt so far.
Specifically, for the HWPREDICT or MHWPREDICT B<RRA>, it sets the intercept and
slope coefficients to unknown. For the SEASONAL B<RRA>, it sets all seasonal
coefficients to unknown. For the DEVSEASONAL B<RRA>, it sets all seasonal
deviation coefficients to unknown. For the FAILURES B<RRA>, it erases the
violation history. Note that reset does not erase past predictions
(the values of the HWPREDICT or MHWPREDICT B<RRA>), predicted deviations (the
values of the DEVPREDICT B<RRA>), or failure history (the values of the 
FAILURES B<RRA>).  This option will function even if not all the listed 
B<RRAs> are present.

Due to the implementation of this option, there is an indirect impact on
other data sources in the RRD. A smoothing algorithm is applied to
SEASONAL and DEVSEASONAL values on a periodic basis. During bootstrap
initialization this smoothing is deferred. For efficiency, the implementation
of smoothing is not data source specific. This means that utilizing
reset for one data source will delay running the smoothing algorithm
for all data sources in the file. This is unlikely to have serious
consequences, unless the data being collected for the non-reset data sources
is unusually volatile during the reinitialization period of the reset
data source.

Use of this tuning option is advised when the behavior of the data source
time series changes in a drastic and permanent manner.

=item B<--step>|B<-t> I<newstep>

Changes the step size of the RRD to newstep.

TODO: add proper documentation

=item B<--daemon>|B<-D> I<address>

B<NOTE>: Because the B<-d> (small letter 'd') option was already taken, this 
function (unlike most other) uses the capital letter 'D' for the one-letter 
option to name the cache daemon.

If given, B<RRDTool> will try to connect to the caching daemon
L<rrdcached> at I<address> and will fail if the connection cannot be
established. If the connection is successfully established the data
for the I<filename> will be flushed before performing the
copy/modify operation. Afterwards the I<filename> will be
forgotten by the cache daemon, so that the next access using the
caching daemon will read the proper structure.

This sequence of operations is designed to achieve a consistent overall 
result with respect to
RRD internal file consistency when using one of the B<DS> or B<RRA> changing 
operations (that is: the resulting file should always be a valid RRD file,
regardless of concurrent updates through the caching daemon).
Regarding data consistency such guarantees are not made: Without external 
synchronization concurrent updates may be lost.

For a list of accepted formats, see the B<-l> option in the L<rrdcached> manual.

=item B<DEL:>I<ds-name>

Every data source named with a DEL specification will be removed.
The resulting RRD will miss both the definition and the data for that 
data source. Multiple DEL specifications are permitted.

=item B<DS:>I<ds-spec>

For every such data source definition (for the exact syntax see the
B<create> command), a new data source will be added to the RRD. Multiple DS 
specifications are permitted.

=item B<DELRRA:>I<index>

Removes the RRA with index I<index>. The index is zero-based, 
that is the very first RRA has index 0.

=item B<RRA:>I<rra-spec>

For every such archive definition (for the exact syntax see the
B<create> command), a new RRA will be added to the output
RRD. Multiple RRA specifications are permitted.

=item B<RRA#>I<index>:[+-=]<number>

Adds/removes or sets the given number of rows for the RRA with index
<index>. The index is zero-based, that is the very first RRA has index 0.

=back

=head1 EXAMPLE 1

C<rrdtool tune data.rrd -h in:100000 -h out:100000 -h through:100000>

Set the minimum required heartbeat for data sources 'in', 'out'
and 'through' to 10'000 seconds which is a little over one day in data.rrd.
This would allow to feed old data from MRTG-2.0 right into
RRDtool without generating *UNKNOWN* entries.

=head1 EXAMPLE 2

C<rrdtool tune monitor.rrd --window-length 5 --failure-threshold 3>

If the FAILURES B<RRA> is implicitly created, the default
window-length is 9 and the default failure-threshold is 7. This
command now defines a failure as 3 or more violations in a temporal
window of 5 time points.

=head1 EXAMPLE 3

C<rrdtool tune some.rrd DEL:a RRA#0:+10>

Delete the data source named B<a> and extend the very first archive by 10 rows.
This will in fact replace the input RRD with a new RRD keeping all existing data.
For most practical use cases this is identical to a real in-place modification.

=head1 AUTHORS

Tobias Oetiker E<lt>tobi@oetiker.chE<gt>, Peter Stamfest E<lt>peter@stamfest.atE<gt>