Diagnostics data management on MTX

The Microwave Tokamak Experiment (MTX) is a magnetic fusion energy research experiment designed to explore electron cyclotron heating, using a free electron laser operating in the microwave range. The diagnostic data from MTX are acquired and processed by a distributed, multivendor, computer network. Each shot of the experiment produces data files containing up to 15 Mbytes of data. Typically half-second shots are taken every five min with 50 to 60 shots taken on a single day. As many as 80 full data shots have been taken on a good day. Data files are created on HP computers running UNIX, HP computers running BASIC, and DEC VAXcluster running VMS. A small portion of the data acquired on the HP systems is immediately stored in a data system on the VAXcluster, but most data are held and processed on the computer on which they were acquired. A commercial database program running on the VAXcluster maintains a history of the data files created for each shot. During the night, data files on all computers are compressed to about one third their original size, and the files on the HP computers are transferred to the VAXcluster. When enough data have accumulated, all data files that have not been previously archived are archived to 8-mm magnetic tape. Once the data are on the VAXcluster, a single defined procedure call may be used to obtain data that were taken on any of the computers in the network