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Wilson_CHEP_Abstract.txt

Heidt, Christopher, 14 February 2012 09:07

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The Memory of MICE, the Configuration Database The configuration database (CDB) is the memory of the Muon Ionisation Cooling Experiment (MICE). 
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Its principle aim was to store temporal data associated with the running conditions of the experiment. This could be data that changed on a per run basis, magnet currents, or more long term data such as cabling, calibration and geometry. The CDB has expanded from its initial use to form an essential part of the MICE state machine as used by the controls and monitoring system. The state of MICE, off, testing, running, etc., dictates the possible states of a hierarchy of sub-systems. The CDB stores information about allowed combinations of states along with allowed settings for all of the controls for every state. Access to the CDB is via a Python API, which communicates with a web-server on the CDB. Master and slave CDBs have been set up in different parts of the site to increase resilience. Both machines have multiple mirrored pair raid arrays, with the data stored on one mirrored pair and the transaction logs stored on another mirrored pair of each machine. Off site backups of the data are also kept. The priority is to ensure availability of the CDB to the control room systems. The master CDB is located in the control area where it is only used by the running experiment. In the event of the failure of the master, the slave can be promoted and the control room services can be switched to use the use the new master. All other access to the CDB, for things like data analysis / reconstruction, is done via the slave which has a up to the minute read only copy of the data. The configuration database stores information concerning the MICE state machine and the running conditions of the MICE experiment in a highly resilient manner. This information is crucial to the running of the experiment and the understanding the data collected by MICE.