Common CWG3 & CWG13 Meeting, 16/04/2014 14:00 60-2-023
 
Present (CWG13): Andrei, Charis, Mohammad, Peter, Raffaele, Ruben, Sylvain, Vasco
Remote (CWG13): Matthias, Ivana, Jens
 
Ideas on conditions DB and data flow (Raffaele) + discussion during the presentation:

• The current calibration produces about 10⁵ files/year, which represents 40 GB/year.
• One third of the files needed for the sim/rec of a given run are automatically updated (i.e. per-run validity, all other objects have long run-range validity).
• Relevant information specific to calibration types is: the validity period (frequence of updates), the statistics needed (how much time to achieve the calibration), and the size of the object (less important).
• Calibrations needed at run-time (for TPC): drift velocity, effective gain, space charge.
• At every instance the "average" space charge distortions correction map is rescaled by the integrated charge of previous 160ms, either from the multiplicity from the FIT or from TPC currents. FLPs associated with TPC can integrate this information and propagate it to the EPNs.
• We can associate the FLP calibration to the raw data since the FLPs can build the sliding window for the calibrations which need it.
• The upper estimate of calibration data rate: 5MB/5ms = 1GB/s. It corresponds to 5% increase with respect to the raw data stream (20GB/s from TPC). Some additional improvements would permit to achieve additional reduction by order of magnitude.
• Do the FLPs read calibration data? No, FLPs only add calibration data to the raw stream.
• DQM is consumer of calibration data.
• For each EPN we need a local copy of the ``static'' calibration information (at initialization, e.g. start of the fill, plus at regular intervals); this (periodic re-)initialization has to be coherent.
• Merging of calibration data among EPNs (similar to event building) requires a calibration dedicated EPN; it might also be needed to reduce the frequency of read/write OCDB accesses.
• The calorimeters are specific case, we have to take into account the 5 calibration steps that are present now.
• The DCS information – pressure, temperature, etc. is needed. One possibility to have it is to provide a DDL link from DCS and record this information in the raw stream.

 
Action list:

• Provide detailed block diagram for the calibration schema (CWG6);
• Provide data flow diagram for the calibration information (CWG6);
• Simulate the data flow that corresponds to calibration (CWG3).