  Business process models describe the way of working in an organization.
Typically, business process models distinguish between the normal flow of work
and exceptions to that normal flow. However, they often present an idealized
view. This means that unexpected exceptions - exceptions that are not modelled
in the business process model - can also occur in practice. This has an effect
on the efficiency of the organization, because information systems are not
developed to handle unexpected exceptions. This paper studies the relation
between the occurrence of exceptions and operational performance. It does this
by analyzing the execution logs of business processes from five organizations,
classifying execution paths as normal or exceptional. Subsequently, it analyzes
the differences between normal and exceptional paths. The results show that
exceptions are related to worse operational performance in terms of a longer
throughput time and that unexpected exceptions relate to a stronger increase in
throughput time than expected exceptions.
