Database usage for the CMS ECAL Laser Monitoring System

The CMS detector at LHC is equipped with a high precision electromagnetic crystal calorimeter (ECAL). The crystals experience a transparency change when exposed to radiation during LHC operation, which recovers in absents of irradiation on the time scale of hours. This change of the crystal response is monitored with a laser system which performs a transparency measurement of each crystal of the ECAL within twenty minutes. The monitoring data is analyzed on a PC farm attached to the central data acquisition system of CMS. After analyzing the raw data, a reduced data set is stored in the Online Master Data Base (OMDS) which is connected to the online computing infrastructure of CMS. The data stored in OMDS, representing the largest data set stored in OMDS for ECAL, contains all necessary information to perform a detailed crystal response monitoring as well as an analysis of the dynamics of the transparency change. For the CMS physics event data reconstruction, only a reduced set of information from the transparency measurement is required. This data is stored in the offline Reconstruction Conditions data base (ORCOF). To transfer the data from the OMDS to ORCOF, the reduced data is transferred to Off-line Reconstruction Conditions DB On-line subset (ORCON) in a procedure known as Online to Offline transfer, which includes various checks for data consistency. In this talk we describe the laser monitoring work flow and the specifics of the data bases usage for the ECAL laser monitoring system. The strategies implemented to optimize the data transfer and to perform quality checks are being presented.