A job monitoring system for the LCG computing grid

Experience with generating simulation data of high energy physics experiments has shown that a job monitoring system (JMS) is essential to understand failures of jobs within the grid. Such a system can give information about the status of the user job as well as the worker node in parallel while a user job is running. It should support the user directly by allowing the user to interact with the running job and should be able to make an automatic error correction. Furthermore, such a system can be extended for an automatic classification of errors which can improve the stability and performance of the grid environment. To increase the acceptance of the grid, a graphical user interface (GUI) has been developed and integrated with the job monitoring system. Both components are currently integrated in the computing environment for generating data for the D0 experiment. In this paper we want to describe the basic components of the job monitoring software.