The most frequently used part of MPI-2 is MPI I/O. Due to the complexity of parallel programming in general, and of handling
parallel I/O in particular, there is a need for tools that support the application development process. There are many situations
where incorrect usage of MPI by the application programmer can be automatically detected. In this paper we describe the MARMOT
tool that uncovers some of these errors and we also analyze to what extent it is possible to do so for MPI I/O.