COMPASS -- DCS

Since October, 2008, the DCS data produced since 2006 is stored in a centralized CERN Oracle database. From 2010 on, the data being produced is streamed to a second Oracle database, that can be used to safely access the DCS data without any direct interference with the production PVSS project.

DCS data from 2003 to 2008

COMPASS took data for physics in 2003, 2004, and since 2006. During this time (including running periods and shutdown periods) the DCS was controling and archiving the values for relevant parameters, like voltages and currents of the detectors' HV systems, temperatures in specific points of the detectors, gas flows in gaseous detectors, the currents in the magnets of the experiment, etc.

The data was originally stored in the RAIMA database format, the one used by PVSS II v.2.12, meaning that, in order to access it, one needed PVSS running. The redesign of the DCS project in view of the experiment's 2nd phase, using a new version of PVSS (v.3.0) dictated the need to store old DCS data in some other format, that will be accessible also in the future. We have chosen to convert the data into Root trees.

DCS data can now be found in the lxplus COMPASS directory, at /afs/cern.ch/compass/detector/calibrations/dcsdata. Alternatively, the data can also be found at CASTOR storage system, under the COMPASS onl account: /castor/cern.ch/user/o/onl/dcs/root

The structure of directories is as follows:

2004

BMS
GEM
HODOS

HOD_HV_Voltage.root
HOD_HV_Current.root
...

Each of these Root files contains a collection of trees. For example, for HOD_HV_Current.root:

The .iMon extension in the name of the trees means monitored current, while the .vMon extension means monitored voltage. Each tree is composed of 2 leaves, one for the value, and another for the timestamp associated with that value.

The absolute timestamp was converted into seconds, using the TDatime function (this function considers time counted from 01/01/1970 00:00:00), in order to save some space. An example is given here (ControlPlots.C), on how to read all the trees in one of these root files and plot corresponding trends, with the x-scale converted back to time.

To get one of these files, you should first, from your afs account in group vy, navigate in castor to locate it:
>nsls -l /castor/cern.ch/user/o/onl/dcs/root/2004
Copy the file into your account. For example:
>rfcp /castor/cern.ch/user/o/onl/dcs/root/2004/HODOS/HOD_HV_Current.root HOD_HV_Current.root
Use ControlPlots.C by editing it and adapting, or your own program, to create the trend plots.