The DOM4 database system Free

The DOM4 database system is designed to manage experimental bulk data, i.e., raw measurements, from large pulsed research devices such as tokamaks. Data are organized in objects, each containing all data from a single measuring point. All objects from an experimental pulse are stored in a single file, the so‐called pulse file. For the ‘‘Rijnhuizen Tokamak Project,’’ the primary user of the DOM4 software, the size of a typical pulse file is a few MBytes and such a file contains in the order of 800 objects. The DOM4 software is optimized for performance, anticipating and exploiting the peculiarities of its application field. The data acquisition takes place using a heterogeneous, distributed computer system, comprising DEC VAXes, MIPS R3000‐based workstations, and a variety of MC680x0 embedded systems. The data in a pulse file are commonly accessed following a nearly Write‐Once‐Read‐Many scenario: After the completion of the data acquisition cycle in the on‐line phase of the experiment, the contents of the pulse file are rarely modified or deleted.