Errors are reported to the application with the error object and by firing the Error event. ErrorConstants fall into two classes: design-time errors and run-time errors. The Error event always fires when any error occurs. When Timeout is 0, however, run-time errors are not thrown back to the container. This allows applications that use only non-blocking operation to localize all error handling in the Error event. To summarize:

Timeout is 0 (non-blocking). All errors are reported via the Error event. Only errors classified as design time errors are also reported back from methods using the error object.

Timeout is not 0 (blocking). All errors are reported via the Error event. All errors occurring within the scope of a method are reported back to the container using the error object.

Errors are marked as INFO or FATAL. An INFO error does not affect the State property. A FATAL error performs an Abort and releases all resources.