First experience in operating the population of the condition databases for the CMS experiment

TL;DR

This paper describes the implementation and initial operational experience of a flexible, object-oriented system for populating condition databases in the CMS experiment, ensuring prompt data availability for online and offline use.

Contribution

It introduces a novel, flexible database population system using POOL-ORA technology and the PopCon package, tailored for CMS's specific needs and tested during cosmic ray test runs.

Findings

System successfully populated condition databases during 2008 test runs.

Ensured immediate online and offline data availability for CMS.

Demonstrated flexibility and reliability of the database population approach.

Abstract

Reliable population of the condition databases is critical for the correct operation of the online selection as well as of the offline reconstruction and analysis of data. We will describe here the system put in place in the CMS experiment to populate the database and make condition data promptly available both online for the high-level trigger and offline for reconstruction. The system, designed for high flexibility to cope with very different data sources, uses POOL-ORA technology in order to store data in an object format that best matches the object oriented paradigm for \texttt{C++} programming language used in the CMS offline software. In order to ensure consistency among the various subdetectors, a dedicated package, PopCon (Populator of Condition Objects), is used to store data online. The data are then automatically streamed to the offline database hence immediately accessible offline worldwide. This mechanism was intensively used during 2008 in the test-runs with cosmic rays. The experience of this first months of operation will be discussed in detail.