Database concepts

The Database Management System (DBMS), which is the central structure of the system, is organized into two major components: one optimized for real-time data and the other for managing long-term Historical data.

The real-time functionality is managed using the RealTime database (RTDB) system. Long-term system history is managed using the Historical database (HDB), also referred to as XIS (eXtended Information System).

The DBMS provides all of the interfaces required to move data between the components. It is structured to gather data, store acquired data, and provide framework for data processing, device control, and internal monitoring of system processes.

The RTDB is specially designed for real-time data processing.

Typically, both configuration data and real-time data from the field instruments are contained in the same RTDB table. For example, in the Analog (Analog) and Rate (Rate) tables, each record (for example, each row) represents the current configuration and state of one device. RTDBs remain fixed in size because the real-time data is constantly flowing through them. The number of records only grows when new devices are configured.

The system continuously scans, or polls, the data sources for new data. This polling takes from several hundred microseconds to several seconds. Every time the system gathers data from the data sources, it populates the RTDB fields. This data only remains in the RTDB until the next update, at which time it is overwritten with fresh data. RealTime data from the RTDB is displayed on the easy eXtended Operator Station (ezXOS) user interface and updated on every scan.