History data collection, retrieving and display in the NSLS control system

This paper presents the history data collection, retrieve and presentation subsystem of our control system. We made every effort to to make the software friendly, convenient and robust. It is widely used and has become a very valuable diagnostic tool. Anyone may start and stop his own history at any data rate up to 20 Hz. The data can be periodically written to disk files or stored in a cyclic ring buffer and dumped to a disk file upon request. All the history data files use the self-contained and self-explanatory standard format. One graphical display program displays all the history data files because of their standard format. In addition to the standard features of a plot program, this display program can display up to 16 devices on both axis, take differences with a reference point, browse the data file by pages or a scroll bar, zoom-in and zoom-out any portion of the plot, do many types of analyses, etc