From: Flemming Videbaek (videbaek@sgs1.hirg.bnl.gov)
Date: Thu Aug 14 2003 - 10:32:49 EDT
As you may have seen Hiro is making the basic calibrations for BB, Inel counters etc for the dAu and pp run-3 data. While discussion this with Hiro i.e. checking what calibration did already exist I will remind you all about the methid the DB uses, and a concern about potential calibration issues/conflict in the DB. The DB was designed (briefly the following way) when finding a valid calibration. a) If one or more calibration exists for a given RUN (in fact time) say 8060 e.g the newest one will be picked. What doies it mean a calibration exists- it means that the validity period of the calibration i.e. validStart to validEnd overlaps the run/time asked for. Assume you have the following situation --rev 1) start 8040 end 8080 --rev 2) start 8060 end 8060 When asking for run 8060 you will get rev2) as you expect. One the other hand if you ask for 8061 you will get 1) since there is only one calibration with overlapping validity period. On the other hand if you ask for 8081 you will get rev2) since this is the newest with the nearest validity time. Now why does this matter - you will say calibrations are only inserted for a given run, or possible with a short number of runs e.g in the case of slewings where multiple run are used. Thats is waht one will hope for- butthis is not the case. What we found were e.g. a calibration for BB slweing covering the run period 7000-8465. Since the new cal are only done for selected runs one would not get the correct calibration, but this specific one inserted with a very long validity period. To resolve the problem we can either a) change the algorithm for picking the calibration to always look for the nearest and newest one, as is in fact done in the script in the DAQ page telling you about . b) modify the validEnd in calibration committed if they are clear too large? and c) MAke sure when you commit new cal they are for single run's only !!! Thus this is also a warning to commit calibration only for one RUN and not for an extended period. Logically if you make say a calibration from multiple runs the natural period is from first run to last run used. Looking specifically what I seen in the DB is that some older calibration too exists than run over long periods which were committed quite early in the DB. example: BB slewing has one ancient cal(for slewing) the covers 3995->5320 and another that covers 5336-> 5581 with about 18 newer revisions in that range. I will thus suspect that some runs e.g. between 5366 to 5581 has been using the old calibrations and not the newer and presumably better except for the specific runno where the calibrations was done. Flemming ------------------------------------------------------ Flemming Videbaek Physics Department Brookhaven National Laboratory tlf: 631-344-4106 fax 631-344-1334 e-mail: videbaek@bnl.gov
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