A. Valassi (CERN)
The migration of the Harp data and software from an Objectivity- based to an Oracle-based data storage solution is reviewed in this presentation. The project, which was successfully completed in January 2004, involved three distinct phases. In the first phase, which profited significantly from the previous COMPASS data migration project, 30 TB of Harp raw event data were migrated in two weeks to a hybrid persistency solution, storing raw event records in standard "flat" files and the corresponding metadata in Oracle as relational tables. In the second phase, the longest to achieve in spite of the relatively limited data volume to migrate, the complex data model of Harp event collections was reimplemented for the Oracle-based solution. The relational schema design and the implementation of read-only navigational access to event collections in the Harp software framework using Oracle are reviewed in detail in the presentation. The third phase was the easiest, as it involved the migration of conditions data (time-varying non-event data) from the Objectivity to the Oracle implementation of a same C++ API, which acted as a screening layer between the data model and its implementation.