FAQ – Databases

SID Monitor uses RRDTool for the management of the databases. This tool handles databases according to the "round robin" scheme. They have predefined fixed sizes, and the newer values are overwritten over the oldest ones.
This FAQ assumes the reader has a good knowledge of RRDTool commands.

Channels Database

Contents

The Channels database stores all channels signal levels. It has a capacity of 31 days. One dataset named sun is defined to store the sun position with an update period of 1 minute.
Each channel has its own dataset. Nominal refresh period of the signal level is set in the Data Acquisition panel.

Example

Here is an example of creation of the Channels database.

	  rrdtool create "D:\...\sid-test.rrd"
	  --start 1147361783 --step 10
	  DS:sun:GAUGE:120:0:8
	  DS:test:GAUGE:20:0:4096
	  RRA:AVERAGE:0.99:1:267840
	  RRA:HWPREDICT:267840:0.50:0.50:8640:3
	  RRA:SEASONAL:8640:0.50:2
	  RRA:DEVSEASONAL:8640:0.50:2
	  RRA:DEVPREDICT:267840:4
	  RRA:FAILURES:267840:7:9:4 
	  

Refresh period (step) is set to 10 seconds. It corresponds to the sampling period of the signal level as defined in the Options menu.
Two datasets are created, sun and test with a GAUGE data type.
For the sun dataset, the heartbeat is set to 120 seconds, meaning that at least one value every two minutes is necessary, otherwise the interval value will be set to Unknown. Nominal update is every minute. Minimum and Maximum values are respectively set to 0 and 8.
For the test dataset, the heartbeat is set to 20 seconds, meaning that at least one value out of two is necessary, otherwise the interval value will be set to Unknown. Minimum and Maximum values are set to 0 and 4096, expressed in mV.
The first archive stores actual values from the 'sun' and the 'test' datasets. It has the AVERAGE consolidation function, with a step parameter of 1, meaning that no average is done. The number of rows (267840) corresponds to the number of 10-seconds intervals in 31 days... The xff parameter is set to 0.99, meaning that 99% of the data may be missing while still validating a given interval.
The subsequent archives HWPREDICT, SEASONAL, DEVSEASONAL, DEVPREDICT and FAILURES are related to the Holt-Winters algorithm. "Alpha", "Beta", "Gamma seasonal" and "Gamma dev seasonal" parameters are set to 0.5. The seasonal period (8640) corresponds to the number of 10-seconds intervals in one day. The window length (9) and the threshold (7) have their default values.

GOES Database

Contents

The GOES database stores all GOES X-ray flux values downloaded from the internet. It has a capacity of 31 days.
It contains three datasets, goes10, goes11 and goes12, corresponding to each source of data. Nominal refresh interval is 1 minute.

Example

Here is an example of creation of the GOES database.

Refresh period (step) is set to 60 seconds. It corresponds to the sampling interval of the X-ray flux data.
Two datasets are created, goesp (Primary GOES data) and goess (Secondary GOES data) with a GAUGE data type. Heartbeat is set to 120 seconds, meaning that at least one value every two minutes is necessary, otherwise the interval value will be set to Unknown. Minimum and Maximum values are not set.
Only one archive is defined. It has the AVERAGE consolidation function, with a step parameter of 1, meaning that no average is done. The number of rows (44640) corresponds to the number of minutes in 31 days... The xff parameter is set to 0.99, meaning that 99% of the data may be missing while still validating a given interval.

	  rrdtool create "D:\...\goes-test.rrd"
	  --start 1144683393 --step 60
	  DS:goesp:GAUGE:120:U:U DS:goess:GAUGE:120:U:U
	  RRA:AVERAGE:0.99:1:44640