The type of exception returned by failed invokation of an MTOSI message request. A coarse grain approach is adopted for capturing exceptions as well. This has the advantage of making the catching of exceptions fairly generic. This is similar to the TMF 814 Corba interface. In the future, each interface operation could implement a specific set of the exceptions. The exception type based on the enumeration A string indicating further details about the exception. It is a free format string filled by the OS. A string indicating further details about the exception. It is a free format string filled by the OS.