Event Logging and Distribution for the BaBar Online System

We discuss the BABAR experiment software and computing infrastructure used for event logging and distribution to prompt reconstruction system. The raw data for typical BABAR events is about 30-50 kB per event. During the data taking a 100 Hz stream of events is collected from a farm of 32 online computers amounting to about 3-5 MB/s. A robust and efficient multi-threaded, TCP/IP based logging manager software was written to serve this purpose. Monitoring of the status of the program is achieved using CORBA. The same program is also used to distribute the logged events to a larger farm of 200 unix processors to process data promptly. This prompt processing involves full reconstruction and calibration programs before final storage in the Objectivity database. We describe the performance of underlying hardware and software, and address scalability of the program.