Under Midas, a run starts when the system receives a Start Transition , and continues until it receives a Stop transition. In the simplest case, this is when the commands "Start" and "Stop" are issued from the ODBedit command. Refer to Run States and Transitions for more details.
- Run Control
- describes how that run may be controlled, including
- where the data is to be stored (e.g. tape),
- on what conditions the run should be allowed to start (e.g. hardware is ready, beam is on)
- when it should stop (e.g. beam goes off, hardware failure).
- informing the user on the progress of the run,
- displaying statistics or history plots,
- sending information or alarm messages to warn the user of any problems.
Fundamental to Run Control and Monitoring is the Online Database (ODB) which contains all of the information for an experiment. Therefore a run control program requires access only to information in the ODB. Programming exactly what data is read during the run falls under Frontend Operation ,and analyzing the data during or after the run is described under Data Analysis.
Run Control Programs
Users must have some way of controlling the experiment (i.e. starting and stopping a run, changing the run parameters etc.) and of determining the progress of the run (e.g. whether the run started successfully, whether data is being taken and saved, and whether any error conditions have occurred).
Several utilities for Run Control are provided in the MIDAS package:
- MIDAS Web Server (mhttpd)
- is the usual choice for experimenters, since it provides a graphical interface, and is used both for run control and monitoring. It has many features not available in odbedit, such as history display, electronic logbook, custom pages and alias-links (see Web Server). However, it has limited functionality as an ODB editor.
- provides a simple command line interface. It is very useful for debugging, is often quicker and simpler to use, and is a fully functional odb editor (hence its name). It has limited monitoring capability.
Other utilities for monitoring are also provided, such as
- a simple monitoring task, and
- which can dump the raw data banks from a running experiment.
Various keys in the ODB can be customized for Run Control. This involves creating and/or editing keys using odbedit or the Web Server . Where the customization is only relevent to mhttpd, it will be described in the appropriate mhttpd section.