Data management in the TJ-II multi-layer database

The handling of TJ-II experimental data is performed by means of several so ftware modules. These modules provide the resources for data capture, data storage and management, data access as well as general-purpose data visuali sation. Here we describe the module related to data storage and management. We begin by introducing the categories in which data can be classified. Th en, we describe the TJ-II data flow through the several file systems involv ed, before discussing the architecture of the TJ-II database. We review the concept of the 'discharge file' and identify the drawbacks that would resu lt from a direct application of this idea to the TJ-II data. In order to ov ercome these drawbacks, we propose alternatives based on our concepts of si gnal family, user work-group and data priority. Finally, we present a model for signal storage. This model is in accordance with the database architec ture and provides a proper framework for managing the TJ-II experimental da ta. In the model, the information is organised in layers and is distributed according to the generality of the information, from the common fields of all signals (first layer), passing through the specific records of signal f amilies (second layer) and reaching the particular information of individua l signals (third layer). (C) 2000 Elsevier Science S.A. All rights reserved .